docs: add color scheme implementation plan

Comprehensive plan with 6 chunks, each containing bite-sized TDD tasks:
- Chunk 1: Theme class and registry
- Chunk 2: Config integration
- Chunk 3: Render pipeline
- Chunk 4: Message gradient integration
- Chunk 5: Color picker UI
- Chunk 6: Integration and validation

Each step includes exact code, test commands, and expected output.

docs/superpowers/plans/2026-03-16-color-scheme-implementation.md

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+# Color Scheme Switcher Implementation Plan
+
+> **For agentic workers:** REQUIRED: Use superpowers:subagent-driven-development (if subagents available) or superpowers:executing-plans to implement this plan. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Implement interactive color theme picker at startup that lets users choose between green, orange, or purple gradients with complementary message queue colors.
+
+**Architecture:** New `themes.py` data module defines Theme class and THEME_REGISTRY. Config adds `ACTIVE_THEME` global set by picker. Render functions read from active theme instead of hardcoded constants. App adds picker UI that mirrors font picker pattern.
+
+**Tech Stack:** Python 3.10+, ANSI 256-color codes, existing terminal I/O utilities
+
+---
+
+## File Structure
+
+| File | Purpose | Change Type |
+|------|---------|------------|
+| `engine/themes.py` | Theme class, THEME_REGISTRY, color codes | Create |
+| `engine/config.py` | ACTIVE_THEME global, set_active_theme() | Modify |
+| `engine/render.py` | Replace GRAD_COLS/MSG_GRAD_COLS with config lookup | Modify |
+| `engine/scroll.py` | Update message gradient call | Modify |
+| `engine/app.py` | pick_color_theme(), call in main() | Modify |
+| `tests/test_themes.py` | Theme class and registry unit tests | Create |
+
+---
+
+## Chunk 1: Theme Data Module
+
+### Task 1: Create themes.py with Theme class and registry
+
+**Files:**
+- Create: `engine/themes.py`
+- Test: `tests/test_themes.py`
+
+- [ ] **Step 1: Write failing test for Theme class**
+
+Create `tests/test_themes.py`:
+
+```python
+"""Test color themes and registry."""
+from engine.themes import Theme, THEME_REGISTRY, get_theme
+
+
+def test_theme_construction():
+    """Theme stores name and gradient lists."""
+    main = ["\033[1;38;5;231m"] * 12
+    msg = ["\033[1;38;5;225m"] * 12
+    theme = Theme(name="Test Green", main_gradient=main, message_gradient=msg)
+
+    assert theme.name == "Test Green"
+    assert theme.main_gradient == main
+    assert theme.message_gradient == msg
+
+
+def test_gradient_length():
+    """Each gradient must have exactly 12 ANSI codes."""
+    for theme_id, theme in THEME_REGISTRY.items():
+        assert len(theme.main_gradient) == 12, f"{theme_id} main gradient wrong length"
+        assert len(theme.message_gradient) == 12, f"{theme_id} message gradient wrong length"
+
+
+def test_theme_registry_has_three_themes():
+    """Registry contains green, orange, purple."""
+    assert len(THEME_REGISTRY) == 3
+    assert "green" in THEME_REGISTRY
+    assert "orange" in THEME_REGISTRY
+    assert "purple" in THEME_REGISTRY
+
+
+def test_get_theme_valid():
+    """get_theme returns Theme object for valid ID."""
+    theme = get_theme("green")
+    assert isinstance(theme, Theme)
+    assert theme.name == "Verdant Green"
+
+
+def test_get_theme_invalid():
+    """get_theme raises KeyError for invalid ID."""
+    with pytest.raises(KeyError):
+        get_theme("invalid_theme")
+
+
+def test_green_theme_unchanged():
+    """Green theme uses original green → magenta colors."""
+    green_theme = get_theme("green")
+    # First color should be white (bold)
+    assert green_theme.main_gradient[0] == "\033[1;38;5;231m"
+    # Last deep green
+    assert green_theme.main_gradient[9] == "\033[38;5;22m"
+    # Message gradient is magenta
+    assert green_theme.message_gradient[9] == "\033[38;5;89m"
+```
+
+Run: `pytest tests/test_themes.py -v`
+Expected: FAIL (module doesn't exist)
+
+- [ ] **Step 2: Create themes.py with Theme class and finalized gradients**
+
+Create `engine/themes.py`:
+
+```python
+"""Color theme definitions and registry."""
+from typing import Optional
+
+
+class Theme:
+    """Encapsulates a color scheme: name, main gradient, message gradient."""
+
+    def __init__(self, name: str, main_gradient: list[str], message_gradient: list[str]):
+        """Initialize theme with display name and gradient lists.
+
+        Args:
+            name: Display name (e.g., "Verdant Green")
+            main_gradient: List of 12 ANSI 256-color codes (white → primary color)
+            message_gradient: List of 12 ANSI codes (white → complementary color)
+        """
+        self.name = name
+        self.main_gradient = main_gradient
+        self.message_gradient = message_gradient
+
+
+# ─── FINALIZED GRADIENTS ──────────────────────────────────────────────────
+# Each gradient: white → primary/complementary, 12 steps total
+# Format: "\033[<brightness>;<color>m" where color is 38;5;<colorcode>
+
+_GREEN_MAIN = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;195m",  # pale white-tint
+    "\033[38;5;123m",    # bright cyan
+    "\033[38;5;118m",    # bright lime
+    "\033[38;5;82m",     # lime
+    "\033[38;5;46m",     # bright green
+    "\033[38;5;40m",     # green
+    "\033[38;5;34m",     # medium green
+    "\033[38;5;28m",     # dark green
+    "\033[38;5;22m",     # deep green
+    "\033[2;38;5;22m",   # dim deep green
+    "\033[2;38;5;235m",  # near black
+]
+
+_GREEN_MESSAGE = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;225m",  # pale pink-white
+    "\033[38;5;219m",    # bright pink
+    "\033[38;5;213m",    # hot pink
+    "\033[38;5;207m",    # magenta
+    "\033[38;5;201m",    # bright magenta
+    "\033[38;5;165m",    # orchid-red
+    "\033[38;5;161m",    # ruby-magenta
+    "\033[38;5;125m",    # dark magenta
+    "\033[38;5;89m",     # deep maroon-magenta
+    "\033[2;38;5;89m",   # dim deep maroon-magenta
+    "\033[2;38;5;235m",  # near black
+]
+
+_ORANGE_MAIN = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;215m",  # pale orange-white
+    "\033[38;5;209m",    # bright orange
+    "\033[38;5;208m",    # vibrant orange
+    "\033[38;5;202m",    # orange
+    "\033[38;5;166m",    # dark orange
+    "\033[38;5;130m",    # burnt orange
+    "\033[38;5;94m",     # rust
+    "\033[38;5;58m",     # dark rust
+    "\033[38;5;94m",     # rust (hold)
+    "\033[2;38;5;94m",   # dim rust
+    "\033[2;38;5;235m",  # near black
+]
+
+_ORANGE_MESSAGE = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;195m",  # pale cyan-white
+    "\033[38;5;33m",     # bright blue
+    "\033[38;5;27m",     # blue
+    "\033[38;5;21m",     # deep blue
+    "\033[38;5;21m",     # deep blue (hold)
+    "\033[38;5;21m",     # deep blue (hold)
+    "\033[38;5;18m",     # navy
+    "\033[38;5;18m",     # navy (hold)
+    "\033[38;5;18m",     # navy (hold)
+    "\033[2;38;5;18m",   # dim navy
+    "\033[2;38;5;235m",  # near black
+]
+
+_PURPLE_MAIN = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;225m",  # pale purple-white
+    "\033[38;5;177m",    # bright purple
+    "\033[38;5;171m",    # vibrant purple
+    "\033[38;5;165m",    # purple
+    "\033[38;5;135m",    # medium purple
+    "\033[38;5;129m",    # purple
+    "\033[38;5;93m",     # dark purple
+    "\033[38;5;57m",     # deep purple
+    "\033[38;5;57m",     # deep purple (hold)
+    "\033[2;38;5;57m",   # dim deep purple
+    "\033[2;38;5;235m",  # near black
+]
+
+_PURPLE_MESSAGE = [
+    "\033[1;38;5;231m",  # white (bold)
+    "\033[1;38;5;226m",  # pale yellow-white
+    "\033[38;5;226m",    # bright yellow
+    "\033[38;5;220m",    # yellow
+    "\033[38;5;220m",    # yellow (hold)
+    "\033[38;5;184m",    # dark yellow
+    "\033[38;5;184m",    # dark yellow (hold)
+    "\033[38;5;178m",    # olive-yellow
+    "\033[38;5;178m",    # olive-yellow (hold)
+    "\033[38;5;172m",    # golden
+    "\033[2;38;5;172m",  # dim golden
+    "\033[2;38;5;235m",  # near black
+]
+
+# ─── THEME REGISTRY ───────────────────────────────────────────────────────
+
+THEME_REGISTRY = {
+    "green": Theme(
+        name="Verdant Green",
+        main_gradient=_GREEN_MAIN,
+        message_gradient=_GREEN_MESSAGE,
+    ),
+    "orange": Theme(
+        name="Molten Orange",
+        main_gradient=_ORANGE_MAIN,
+        message_gradient=_ORANGE_MESSAGE,
+    ),
+    "purple": Theme(
+        name="Violet Purple",
+        main_gradient=_PURPLE_MAIN,
+        message_gradient=_PURPLE_MESSAGE,
+    ),
+}
+
+
+def get_theme(theme_id: str) -> Theme:
+    """Retrieve a theme by ID.
+
+    Args:
+        theme_id: One of "green", "orange", "purple"
+
+    Returns:
+        Theme object
+
+    Raises:
+        KeyError: If theme_id not found in registry
+    """
+    if theme_id not in THEME_REGISTRY:
+        raise KeyError(f"Unknown theme: {theme_id}. Available: {list(THEME_REGISTRY.keys())}")
+    return THEME_REGISTRY[theme_id]
+```
+
+- [ ] **Step 3: Run tests to verify they pass**
+
+Run: `pytest tests/test_themes.py -v`
+Expected: PASS (all 6 tests)
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add engine/themes.py tests/test_themes.py
+git commit -m "feat: create Theme class and registry with finalized color gradients
+
+- Define Theme class to encapsulate name and main/message gradients
+- Create THEME_REGISTRY with green, orange, purple themes
+- Each gradient has 12 ANSI 256-color codes finalized
+- Complementary color pairs: green/magenta, orange/blue, purple/yellow
+- Add get_theme() lookup with error handling
+- Add comprehensive unit tests"
+```
+
+---
+
+## Chunk 2: Config Integration
+
+### Task 2: Add ACTIVE_THEME global and set_active_theme() to config.py
+
+**Files:**
+- Modify: `engine/config.py:1-30`
+- Test: `tests/test_config.py` (expand existing)
+
+- [ ] **Step 1: Write failing tests for config changes**
+
+Add to `tests/test_config.py`:
+
+```python
+def test_active_theme_initially_none():
+    """ACTIVE_THEME is None before initialization."""
+    # This test may fail if config is already initialized
+    # We'll set it to None first for testing
+    import engine.config
+    engine.config.ACTIVE_THEME = None
+    assert engine.config.ACTIVE_THEME is None
+
+
+def test_set_active_theme_green():
+    """set_active_theme('green') sets ACTIVE_THEME to green theme."""
+    from engine.config import set_active_theme
+    from engine.themes import get_theme
+
+    set_active_theme("green")
+
+    assert config.ACTIVE_THEME is not None
+    assert config.ACTIVE_THEME.name == "Verdant Green"
+    assert config.ACTIVE_THEME == get_theme("green")
+
+
+def test_set_active_theme_default():
+    """set_active_theme() with no args defaults to green."""
+    from engine.config import set_active_theme
+
+    set_active_theme()
+
+    assert config.ACTIVE_THEME.name == "Verdant Green"
+
+
+def test_set_active_theme_invalid():
+    """set_active_theme() with invalid ID raises KeyError."""
+    from engine.config import set_active_theme
+
+    with pytest.raises(KeyError):
+        set_active_theme("invalid")
+```
+
+Run: `pytest tests/test_config.py -v`
+Expected: FAIL (functions don't exist yet)
+
+- [ ] **Step 2: Add ACTIVE_THEME global and set_active_theme() to config.py**
+
+Edit `engine/config.py`, add after line 30 (after `_resolve_font_path` function):
+
+```python
+# ─── COLOR THEME ──────────────────────────────────────────────────────────
+ACTIVE_THEME = None  # set by set_active_theme() after picker
+
+
+def set_active_theme(theme_id: str = "green"):
+    """Set the active color theme. Defaults to 'green' if not specified.
+
+    Args:
+        theme_id: One of "green", "orange", "purple"
+
+    Raises:
+        KeyError: If theme_id is invalid
+    """
+    global ACTIVE_THEME
+    from engine import themes
+    ACTIVE_THEME = themes.get_theme(theme_id)
+```
+
+- [ ] **Step 3: Remove hardcoded GRAD_COLS and MSG_GRAD_COLS from render.py**
+
+Edit `engine/render.py`, find and delete lines 20-49 (the hardcoded gradient arrays):
+
+```python
+# DELETED:
+# GRAD_COLS = [...]
+# MSG_GRAD_COLS = [...]
+```
+
+- [ ] **Step 4: Run tests to verify they pass**
+
+Run: `pytest tests/test_config.py::test_active_theme_initially_none -v`
+Run: `pytest tests/test_config.py::test_set_active_theme_green -v`
+Run: `pytest tests/test_config.py::test_set_active_theme_default -v`
+Run: `pytest tests/test_config.py::test_set_active_theme_invalid -v`
+
+Expected: PASS (all 4 new tests)
+
+- [ ] **Step 5: Verify existing config tests still pass**
+
+Run: `pytest tests/test_config.py -v`
+
+Expected: PASS (all existing + new tests)
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add engine/config.py tests/test_config.py
+git commit -m "feat: add ACTIVE_THEME global and set_active_theme() to config
+
+- Add ACTIVE_THEME global (initialized to None)
+- Add set_active_theme(theme_id) function with green default
+- Remove hardcoded GRAD_COLS and MSG_GRAD_COLS (move to themes.py)
+- Add comprehensive tests for theme setting"
+```
+
+---
+
+## Chunk 3: Render Pipeline Integration
+
+### Task 3: Update render.py to use config.ACTIVE_THEME
+
+**Files:**
+- Modify: `engine/render.py:15-220`
+- Test: `tests/test_render.py` (expand existing)
+
+- [ ] **Step 1: Write failing test for lr_gradient with theme**
+
+Add to `tests/test_render.py`:
+
+```python
+def test_lr_gradient_uses_active_theme(monkeypatch):
+    """lr_gradient uses config.ACTIVE_THEME when cols=None."""
+    from engine import config, render
+    from engine.themes import get_theme
+
+    # Set orange theme
+    config.set_active_theme("orange")
+
+    # Create simple rows
+    rows = ["test row"]
+    result = render.lr_gradient(rows, offset=0, cols=None)
+
+    # Result should start with first color from orange main gradient
+    assert result[0].startswith("\033[1;38;5;231m")  # white (same for all)
+
+
+def test_lr_gradient_fallback_when_no_theme(monkeypatch):
+    """lr_gradient uses fallback when ACTIVE_THEME is None."""
+    from engine import config, render
+
+    # Clear active theme
+    config.ACTIVE_THEME = None
+
+    rows = ["test row"]
+    result = render.lr_gradient(rows, offset=0, cols=None)
+
+    # Should not crash and should return something
+    assert result is not None
+    assert len(result) > 0
+
+
+def test_default_green_gradient_length():
+    """_default_green_gradient returns 12 colors."""
+    from engine import render
+
+    colors = render._default_green_gradient()
+    assert len(colors) == 12
+```
+
+Run: `pytest tests/test_render.py::test_lr_gradient_uses_active_theme -v`
+Expected: FAIL (function signature doesn't match)
+
+- [ ] **Step 2: Update lr_gradient() to use config.ACTIVE_THEME**
+
+Edit `engine/render.py`, find the `lr_gradient()` function (around line 194) and update it:
+
+```python
+def lr_gradient(rows, offset, cols=None):
+    """
+    Render rows through a left-to-right color sweep.
+
+    Args:
+        rows: List of text rows to colorize
+        offset: Gradient position offset (for animation)
+        cols: Optional list of color codes. If None, uses active theme.
+
+    Returns:
+        List of colorized rows
+    """
+    if cols is None:
+        from engine import config
+        cols = (
+            config.ACTIVE_THEME.main_gradient
+            if config.ACTIVE_THEME
+            else _default_green_gradient()
+        )
+
+    # ... rest of function unchanged ...
+```
+
+- [ ] **Step 3: Add _default_green_gradient() fallback function**
+
+Add to `engine/render.py` before `lr_gradient()`:
+
+```python
+def _default_green_gradient():
+    """Fallback green gradient (original colors) for initialization."""
+    return [
+        "\033[1;38;5;231m",  # white (bold)
+        "\033[1;38;5;195m",  # pale white-tint
+        "\033[38;5;123m",    # bright cyan
+        "\033[38;5;118m",    # bright lime
+        "\033[38;5;82m",     # lime
+        "\033[38;5;46m",     # bright green
+        "\033[38;5;40m",     # green
+        "\033[38;5;34m",     # medium green
+        "\033[38;5;28m",     # dark green
+        "\033[38;5;22m",     # deep green
+        "\033[2;38;5;22m",   # dim deep green
+        "\033[2;38;5;235m",  # near black
+    ]
+
+
+def _default_magenta_gradient():
+    """Fallback magenta gradient (original message colors) for initialization."""
+    return [
+        "\033[1;38;5;231m",  # white (bold)
+        "\033[1;38;5;225m",  # pale pink-white
+        "\033[38;5;219m",    # bright pink
+        "\033[38;5;213m",    # hot pink
+        "\033[38;5;207m",    # magenta
+        "\033[38;5;201m",    # bright magenta
+        "\033[38;5;165m",    # orchid-red
+        "\033[38;5;161m",    # ruby-magenta
+        "\033[38;5;125m",    # dark magenta
+        "\033[38;5;89m",     # deep maroon-magenta
+        "\033[2;38;5;89m",   # dim deep maroon-magenta
+        "\033[2;38;5;235m",  # near black
+    ]
+```
+
+- [ ] **Step 4: Run tests to verify they pass**
+
+Run: `pytest tests/test_render.py::test_lr_gradient_uses_active_theme -v`
+Run: `pytest tests/test_render.py::test_lr_gradient_fallback_when_no_theme -v`
+Run: `pytest tests/test_render.py::test_default_green_gradient_length -v`
+
+Expected: PASS (all 3 new tests)
+
+- [ ] **Step 5: Run full render test suite**
+
+Run: `pytest tests/test_render.py -v`
+
+Expected: PASS (existing tests may need adjustment for mocking)
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add engine/render.py tests/test_render.py
+git commit -m "feat: update lr_gradient to use config.ACTIVE_THEME
+
+- Update lr_gradient(cols=None) to check config.ACTIVE_THEME
+- Add _default_green_gradient() and _default_magenta_gradient() fallbacks
+- Fallback used when ACTIVE_THEME is None (non-interactive init)
+- Add tests for theme-aware and fallback gradient rendering"
+```
+
+---
+
+## Chunk 4: Message Gradient Integration
+
+### Task 4: Update scroll.py to use message gradient from config
+
+**Files:**
+- Modify: `engine/scroll.py:85-95`
+- Test: existing `tests/test_scroll.py`
+
+- [ ] **Step 1: Locate message gradient calls in scroll.py**
+
+Run: `grep -n "MSG_GRAD_COLS\|lr_gradient_opposite" /Users/genejohnson/Dev/mainline/engine/scroll.py`
+
+Expected: Should find line(s) where `MSG_GRAD_COLS` or similar is used
+
+- [ ] **Step 2: Update scroll.py to use theme message gradient**
+
+Edit `engine/scroll.py`, find the line that uses message gradients (around line 89 based on spec) and update:
+
+Old code:
+```python
+# Some variation of:
+rows = lr_gradient(rows, offset, MSG_GRAD_COLS)
+```
+
+New code:
+```python
+from engine import config
+msg_cols = (
+    config.ACTIVE_THEME.message_gradient
+    if config.ACTIVE_THEME
+    else render._default_magenta_gradient()
+)
+rows = lr_gradient(rows, offset, msg_cols)
+```
+
+Or use the helper approach (create `msg_gradient()` in render.py):
+
+```python
+def msg_gradient(rows, offset):
+    """Apply message (ntfy) gradient using theme complementary colors."""
+    from engine import config
+    cols = (
+        config.ACTIVE_THEME.message_gradient
+        if config.ACTIVE_THEME
+        else _default_magenta_gradient()
+    )
+    return lr_gradient(rows, offset, cols)
+```
+
+Then in scroll.py:
+```python
+rows = render.msg_gradient(rows, offset)
+```
+
+- [ ] **Step 3: Run existing scroll tests**
+
+Run: `pytest tests/test_scroll.py -v`
+
+Expected: PASS (existing functionality unchanged)
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add engine/scroll.py engine/render.py
+git commit -m "feat: update scroll.py to use theme message gradient
+
+- Replace MSG_GRAD_COLS reference with config.ACTIVE_THEME.message_gradient
+- Use fallback magenta gradient when theme not initialized
+- Ensure ntfy messages render in complementary color from selected theme"
+```
+
+---
+
+## Chunk 5: Color Picker UI
+
+### Task 5: Create pick_color_theme() function in app.py
+
+**Files:**
+- Modify: `engine/app.py:1-300`
+- Test: manual/integration (interactive)
+
+- [ ] **Step 1: Write helper functions for color picker UI**
+
+Edit `engine/app.py`, add before `pick_font_face()` function:
+
+```python
+def _draw_color_picker(themes_list, selected):
+    """Draw the color theme picker menu."""
+    import sys
+    from engine.terminal import CLR, W_GHOST, G_HI, G_DIM, tw
+
+    print(CLR, end="")
+    print()
+    print(f"  {G_HI}▼ COLOR THEME{W_GHOST} ─ ↑/↓ or j/k to move, Enter/q to select{G_DIM}")
+    print(f"  {W_GHOST}{'─' * (tw() - 4)}\n")
+
+    for i, (theme_id, theme) in enumerate(themes_list):
+        prefix = "  ▶ " if i == selected else "    "
+        color = G_HI if i == selected else ""
+        reset = "" if i == selected else W_GHOST
+        print(f"{prefix}{color}{theme.name}{reset}")
+
+    print()
+```
+
+- [ ] **Step 2: Create pick_color_theme() function**
+
+Edit `engine/app.py`, add after helper function:
+
+```python
+def pick_color_theme():
+    """Interactive color theme picker. Defaults to 'green' if not TTY."""
+    import sys
+    import termios
+    import tty
+    from engine import config, themes
+
+    # Non-interactive fallback: use green
+    if not sys.stdin.isatty():
+        config.set_active_theme("green")
+        return
+
+    themes_list = list(themes.THEME_REGISTRY.items())
+    selected = 0
+
+    fd = sys.stdin.fileno()
+    old_settings = termios.tcgetattr(fd)
+    try:
+        tty.setcbreak(fd)
+        while True:
+            _draw_color_picker(themes_list, selected)
+            key = _read_picker_key()
+            if key == "up":
+                selected = max(0, selected - 1)
+            elif key == "down":
+                selected = min(len(themes_list) - 1, selected + 1)
+            elif key == "enter":
+                break
+            elif key == "interrupt":
+                raise KeyboardInterrupt
+    finally:
+        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
+
+    selected_theme_id = themes_list[selected][0]
+    config.set_active_theme(selected_theme_id)
+
+    theme_name = themes_list[selected][1].name
+    print(f"  {G_DIM}> using {theme_name}{RST}")
+    time.sleep(0.8)
+    print(CLR, end="")
+    print(CURSOR_OFF, end="")
+    print()
+```
+
+- [ ] **Step 3: Update main() to call pick_color_theme() before pick_font_face()**
+
+Edit `engine/app.py`, find the `main()` function and locate where `pick_font_face()` is called (around line 265). Add before it:
+
+```python
+def main():
+    # ... existing signal handler setup ...
+
+    pick_color_theme()  # NEW LINE - before font picker
+    pick_font_face()
+
+    # ... rest of main unchanged ...
+```
+
+- [ ] **Step 4: Manual test - run in interactive terminal**
+
+Run: `python3 mainline.py`
+
+Expected:
+- See color theme picker menu before font picker
+- Can navigate with ↑/↓ or j/k
+- Can select with Enter or q
+- Selected theme applies to scrolling headlines
+- Can select different themes and see colors change
+
+- [ ] **Step 5: Manual test - run in non-interactive environment**
+
+Run: `echo "" | python3 mainline.py`
+
+Expected:
+- No color picker menu shown
+- Defaults to green theme
+- App runs without error
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add engine/app.py
+git commit -m "feat: add pick_color_theme() UI and integration
+
+- Create _draw_color_picker() to render menu
+- Create pick_color_theme() function mirroring font picker pattern
+- Integrate into main() before font picker
+- Fallback to green theme in non-interactive environments
+- Support arrow keys and j/k navigation"
+```
+
+---
+
+## Chunk 6: Integration & Validation
+
+### Task 6: End-to-end testing and cleanup
+
+**Files:**
+- Test: All modified files
+- Verify: App functionality
+
+- [ ] **Step 1: Run full test suite**
+
+Run: `pytest tests/ -v`
+
+Expected: PASS (all tests, including new ones)
+
+- [ ] **Step 2: Run linter**
+
+Run: `ruff check engine/ mainline.py`
+
+Expected: No errors (fix any style issues)
+
+- [ ] **Step 3: Manual integration test - green theme**
+
+Run: `python3 mainline.py`
+
+Then select "Verdant Green" from picker.
+
+Expected:
+- Headlines render in green → deep green
+- ntfy messages render in magenta gradient
+- Both work correctly during streaming
+
+- [ ] **Step 4: Manual integration test - orange theme**
+
+Run: `python3 mainline.py`
+
+Then select "Molten Orange" from picker.
+
+Expected:
+- Headlines render in orange → deep orange
+- ntfy messages render in blue gradient
+- Colors are visually distinct from green
+
+- [ ] **Step 5: Manual integration test - purple theme**
+
+Run: `python3 mainline.py`
+
+Then select "Violet Purple" from picker.
+
+Expected:
+- Headlines render in purple → deep purple
+- ntfy messages render in yellow gradient
+- Colors are visually distinct from green and orange
+
+- [ ] **Step 6: Test poetry mode with color picker**
+
+Run: `python3 mainline.py --poetry`
+
+Then select "orange" from picker.
+
+Expected:
+- Poetry mode works with color picker
+- Colors apply to poetry rendering
+
+- [ ] **Step 7: Test code mode with color picker**
+
+Run: `python3 mainline.py --code`
+
+Then select "purple" from picker.
+
+Expected:
+- Code mode works with color picker
+- Colors apply to code rendering
+
+- [ ] **Step 8: Verify acceptance criteria**
+
+✓ Color picker displays 3 theme options at startup
+✓ Selection applies to all headline and message gradients
+✓ Boot UI (title, status) uses hardcoded green (not theme)
+✓ Scrolling headlines and ntfy messages use theme gradients
+✓ No persistence between runs (each run picks fresh)
+✓ Non-TTY environments default to green without error
+✓ Architecture supports future random/animation modes
+✓ All gradient color codes finalized with no TBD values
+
+- [ ] **Step 9: Final commit**
+
+```bash
+git add -A
+git commit -m "feat: color scheme switcher implementation complete
+
+Closes color-pick feature with:
+- Three selectable color themes (green, orange, purple)
+- Interactive menu at startup (mirrors font picker UI)
+- Complementary colors for ntfy message queue
+- Fallback to green in non-interactive environments
+- All tests passing, manual validation complete"
+```
+
+- [ ] **Step 10: Create feature branch PR summary**
+
+```
+## Color Scheme Switcher
+
+Implements interactive color theme selection for Mainline news ticker.
+
+### What's New
+- 3 color themes: Verdant Green, Molten Orange, Violet Purple
+- Interactive picker at startup (↑/↓ or j/k, Enter to select)
+- Complementary gradients for ntfy messages (magenta, blue, yellow)
+- Fresh theme selection each run (no persistence)
+
+### Files Changed
+- `engine/themes.py` (new)
+- `engine/config.py` (ACTIVE_THEME, set_active_theme)
+- `engine/render.py` (theme-aware gradients)
+- `engine/scroll.py` (message gradient integration)
+- `engine/app.py` (pick_color_theme UI)
+- `tests/test_themes.py` (new theme tests)
+- `README.md` (documentation)
+
+### Acceptance Criteria
+All met. App fully tested and ready for merge.
+```
+
+---
+
+## Testing Checklist
+
+- [ ] Unit tests: `pytest tests/test_themes.py -v`
+- [ ] Unit tests: `pytest tests/test_config.py -v`
+- [ ] Unit tests: `pytest tests/test_render.py -v`
+- [ ] Full suite: `pytest tests/ -v`
+- [ ] Linting: `ruff check engine/ mainline.py`
+- [ ] Manual: Green theme selection
+- [ ] Manual: Orange theme selection
+- [ ] Manual: Purple theme selection
+- [ ] Manual: Poetry mode with colors
+- [ ] Manual: Code mode with colors
+- [ ] Manual: Non-TTY fallback
+
+---
+
+## Notes
+
+- `themes.py` is data-only; never import config or render to prevent cycles
+- `ACTIVE_THEME` initialized to None; guaranteed non-None before stream() via pick_color_theme()
+- Font picker UI remains hardcoded green; title/subtitle use G_HI/G_DIM constants (not theme)
+- Message gradients use complementary colors; lookup in scroll.py
+- Each gradient has 12 colors; verify length in tests
+- No persistence; fresh picker each run