What color signaling device is NOT permitted on the rear of a vehicle?

The use of signaling devices on the rear of a vehicle is strictly regulated to ensure safety and effective communication with other road users. The correct answer indicates that a green signaling device is not permitted on the rear of a vehicle.

This is primarily because green lights are commonly associated with traffic control devices, indicating 'go' or 'proceed'. Allowing green lights on the back of a vehicle could lead to confusion among drivers, as it may be misinterpreted as a signal to proceed, which is not the intent for rear-facing signals.

In contrast, red lights are universally understood as warning lights and are typically used for brake lights. Amber and yellow lights are allowed as caution signals and can be used for indicating a slowdown or warning other drivers of a hazard. Thus, the prohibition of green lights helps maintain clarity and consistency in signaling, which is vital for road safety.