Why are traffic lights red, yellow, and green?
The short answer
Red, yellow, and green are shared signals for road users. Red means stop, yellow warns that the signal is changing, and green generally permits movement in the indicated direction.
Why colors help
Signals must be recognizable from a distance and should communicate even when people cannot read words. Standardizing colors and sequences makes an intersection easier for drivers and pedestrians to predict.
Yellow does not mean “speed up”
Yellow warns that the green phase is ending and a red indication will appear. It is not an invitation to enter an intersection recklessly. Always follow the traffic rules where you are driving or walking.