Colors of traffic lights
The most common colors used in traffic lights are red, amber (yellow), and green. Red typically means stop or high level of danger; amber typically means caution; and green typically means proceed with care.
Usually, the red light contains some orange in its hue, and the green light contains some blue, to provide some support for people with red-green color blindness. In the UK, traffic lights typically have a white reflective border, which enables color blind users, during the hours of darkness, to distinguish the lights from other similarly-colored street or automobile lights, and to allow them to distinguish the lights by vertical position.