Which color of sign typically denotes a prohibition or instruction?

In traffic signage, a red sign is primarily used to indicate prohibitions or mandatory instructions that drivers must follow. This color is universally associated with stop signs, yield signs, and signs indicating no entry or other restrictions. The intense visibility of red makes it effective in grabbing the attention of motorists and signaling the importance of adhering to the instruction, such as stopping or not proceeding in a certain direction.

Other colors have different meanings: yellow often indicates caution or warning, which signals that there may be hazards ahead but does not necessarily prohibit any action. Blue is typically used for informative signs, such as those indicating services or facilities available to drivers, while green typically indicates directional information, guiding drivers on routes and exits. Therefore, red is the definitive choice when it comes to indicating prohibitive actions on the road.