Why do screen night lights that shift the color red work? Why red instead of some other color?

Our retinas are linked up to the portion of the brain that deals with circadian cycles. We evolved to feel more wakeful upon exposure to blue light because that's the color of the sky at midday. Our brains associate red light with sunset, a time where humans have adapted to feel sleepy as opposed to wakeful.

If humans instead evolved on Mars, assuming the lack of an atmosphere and magnetosphere was not an issue, this would be the opposite! Martians would feel more awake on exposure to warmer colored light and sleepy on exposure to blue light, since on Mars, the sunsets are blue!