docs: Fix "Turn the speed blue" tutorial for Raylib UI

[logesh45]

Fix "Turn the speed blue" tutorial for current Raylib UI

Problem: The getting started guide "Turn the speed blue" was outdated and referenced the old Qt-based UI code that no longer exists in openpilot.

Solution: Updated the tutorial to work with the current Raylib-based UI system.

Changes Made

• Updated file path from selfdrive/ui/qt/onroad/hud.cc to selfdrive/ui/onroad/hud_renderer.py
• Replaced C++/Qt code example with current Python/Raylib implementation
• Updated search command to find _draw_current_speed function
• Changed color modification instructions from QColor to COLORS.white
• Added proper color definition for the blue color example

Verification

• ✅ Confirmed current code uses rl.draw_text_ex at line 175 in hud_renderer.py
• ✅ Verified the updated search command finds the correct function
• ✅ Tested that the new instructions work with the Raylib API

Impact

This fix removes a critical barrier for new contributors trying to follow the getting started guide. The previous tutorial would immediately fail with file not found errors and incorrect syntax examples.

Files changed:

• docs/how-to/turn-the-speed-blue.md

[github-actions]

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[TheSecurityDev]

Rebuilding is no longer required with Raylib

[logesh45]

Yes, you are right! updated it.

[Copilot]

Pull request overview

This PR updates the "Turn the speed blue" tutorial from the deprecated Qt/C++ UI implementation to the current Raylib/Python implementation. The update is essential for new contributors following the getting started guide, as the previous version referenced non-existent files and outdated code.

Key Changes

• Updated file paths and references from selfdrive/ui/qt/onroad/hud.cc (C++) to selfdrive/ui/onroad/hud_renderer.py (Python)
• Replaced Qt/C++ code examples with Raylib/Python equivalents
• Changed execution commands from compiled binary (selfdrive/ui/ui) to Python script (./selfdrive/ui/ui.py)

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[royjr]

we should add BIG=1 or do mici instead or both