Why are emergency lights red and blue (sometimes one or the other and not both)? Who decided these colors were the most effective for warning of an emergency?
by 
Molden Molt
ANSWERS: 2
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In the 1970's, they did several studies and found that red and blue are the most visible to the human eye. Red is more visible during the day and blue is more visible at night. That is why both colors are used. Some states, like California, have certain colors for the police and others. Only the police are allowed to have blue lights. Fire and EMS can only use red lights, but the police use both red and blue. Tow trucks, construction, etc use orange or amber lights. In many states, the police only use blue lights and no red.
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All 5 emergency services in the UK use blue lights. Going to an emergency is called 'blues and twos' (blue lights flashing and 2 tone siren. The siren has changed now, but the phrase is still used.). As I've been down marked and re-read my answer, I'll actually answer the question =) In the UK, we don't use red lights as red is the first colour you loose with colour blindness and blue is one of the last. All flashing lights should grab your attention to warn you of a problem/potential trouble ahead (think of rail road crossings). I'm unsure who decided that emergeny light should be the colour that they are or when this happened, but my parents (who are both in their 80's) remember seeing blur lights on police cars in 1930's.
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