What is the required color of stop lamps?

The required color of stop lamps being red or amber is based on safety regulations aimed at ensuring that the signals of a vehicle are easily recognizable to other drivers. Stop lamps must primarily be red because this color universally indicates a stop or caution, making it clear to others on the road what action is required. The addition of amber as an allowable color provides flexibility while still maintaining a clear visual cue that a vehicle is stopping. This regulation helps prevent accidents by ensuring consistent and recognizable signals across all vehicles, thus improving overall road safety.

Other colors like green, which typically indicates go, or blue and white, which are more commonly associated with emergency vehicles, would not effectively convey the intended warning to other drivers. Therefore, the specification of red or amber is crucial for effective communication between vehicles on the roadway.