system/ui: fix rapid path color transition by correcting hardcoded increment

[deanlee]

The path color transition between throttle and no-throttle states was completing too quickly (~0.17 seconds instead of the intended 0.5 seconds). This was caused by a hardcoded increment of 0.1, designed for 20 FPS, which became too fast at the current 60 FPS.

This PR fixes the transition duration to achieve the intended 0.5 seconds by adjusting the increment based on the frame rate. Additionally, it optimizes the color blending function for better performance.

Changes:

• Fixed Transition Duration: Adjusted the hardcoded increment (from 0.1) to scale with the frame rate (60 FPS), ensuring a smooth 0.5-second transition.
• Optimized Color Blending: Modified the color blending function to reuse an existing array instead of creating a new list each frame, reducing memory allocation overhead.