Emergency lights are meant to send a warning message to motorists, pedestrians, emergency personnel, or medical personnel. Emergency light colors are selected based on the physical or psychological response required, as well as on how easy the color is to see from a distance or in the dark. The most prevalent emergency light colors are red, blue, yellow, and white.
Red
Red lights provoke a sense of imminent danger in the U.S.
In the U.S., red is usually the first emergency light color choice. Culturally, red is perceived to be a warning light color, and provokes a sense of alarm. For example, stoplights and stop signs in the U.S. are colored red. According to PoliceOne.com, red is easier to see during the day than at night, so red is a good choice for daytime emergency use.
Blue
Blue emergency lights are especially effective after dark.
Blue is another emergency light color choice. Blue is especially effective for nighttime use because it is easy to see from a distance in the dark, according to PoliceOne.com. In the U.S., blue is the color of choice for emergency call boxes on college campuses and at roadsides. In most of western Europe, blue is the predominant color for police, fire, and other emergency vehicles.
Yellow/Amber
Amber indicates caution, and can be used in combination with other colors.
Yellow, or amber, is also perceived to warn of imminent hazard. In the U.S., amber is often one of the colors used on police cars. According to PoliceOne.com, amber can be used effectively without red or blue, to warn cars away from a police car stopped at the side of the road. In North America, amber is used for construction and utility trucks or vehicles. In the U.S., amber lighting is often used to warn motorists of temporary lane closures.
White
White is an excellent choice for emergency lights, because it is highly visible. On the other hand, white light does not usually elicit a response of alarm. White light is typically used in concert with other colors, such as red or blue, to denote emergency. In Europe, white is typically used along with blue on emergency vehicles. In the U.S., white may be included as an optional color, along with red, blue, and amber on police vehicles. White lights are also used in the U.S. for roadway signs that warn of unusual traffic conditions.
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