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They are "Confirmation Lights" which are the WHITE or BLUE light located directly above a Traffic Signal and are utilised by the Police to detect "Red Light Runners".It is "lit" when the lights are on Red.This allows the Police to see if anyone has run the red light.
I'm not sure that blue traffic lights are real. However, a blue light behind you means you just got pulled over.
To help people with colorblindness the "green" light has a mixture of green and blue. I think they the new lights have more blue than the older ones.
It means that they are a Cyberguide
red and blue light differ in wave length because blue lights have shorter wave length than red light and shorter wave length are good for plants germination.
I have a pink porch light up for breast cancer awareness after recently losing someone close to me.... Green in November to honor our vets blue when a police officer is murdered to honor our men in blue.... Purple for domestic violence awareness
yellow-green
white light carries a long distance, especially at night. Using blue lenses on lights decreases the distance light can be seen, helping to conceal position.
Cyan light results. Green and blue and red lights are all primary colors of light. Because red is not part of cyan light, cyan and red light are complementary colors.
The blue light that is used in restaurants does not actually kill the flies they just attract them to an electrifier. These lights can be bought anywhere.
The light on a mouse does not have to be red. Some computer mice have blue lights, it just depends on which colour light the manufacturer chooses.