On the positive side： Your gray box cleverly embeds the core control logic into the "road sign" system, completely breaking the traditional UI floating feeling. Players control vehicles through directional signs in the scene, retaining the immersion of an open world while achieving natural guidance of functional entrances. This kind of detail processing can be considered a stroke of genius.
However, I have some suggestions: Although yellow blue color collision has high contrast, it can easily cause visual fatigue during the gray box stage. Perhaps you can lower the saturation: change the pure yellow color to "beige+gray", shift the blue color to # 4682B4, and reduce the fluorescence. Even in the next stage of development, the color scheme will be dynamically adjusted based on weather/time - bright yellow blue will be used on sunny days, and a gradient of cool white and deep blue will be used on rainy nights. This is a good example: the "orange background black text" warning sign logic of German traffic signs highlights the core functional areas (such as danger warnings) with "amber gold" and retains low saturation blue for auxiliary information (such as navigation).