The use of **reflective paints** on vehicles is **prohibited**, unless they are **expressly authorized**. This is because any element that may affect the visibility or perception of the vehicle on the road must be regulated to ensure road safety.

- **Visibility while driving**: It is crucial for drivers to have a clear view of their surroundings. Therefore, it is prohibited to use elements that may obstruct visibility, such as films or stickers on the windows. Similarly, unauthorized reflective paints could alter the perception of other drivers.

- **Retro-reflectors**: These devices reflect light to improve the visibility of the vehicle. They are regulated in terms of their color and location, ensuring they fulfill their function without causing confusion or glare. Unauthorized reflective paints could interfere with this regulation.

In summary, any modification that affects the visibility or perception of the vehicle, such as reflective paints, must be authorized to ensure it does not compromise road safety.