Why the Danger Signals are red in Colour ?
That red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a color. Therefore blue which has the least wavelength of all the visible radiations is scattered the most and red which has the highest wavelength of all the colors we can see is scattered the least. So red light is able to travel the longest distance through fog, rain, and the alike. Also, red is a color we inherently perceive as one that is associated with danger. I guess it has been genetically programmed as hot objects are red in color and also red is the color of blood. These reasons make danger signals the most effective when they are painted in red.
Red colour is used in danger signals due to the following reasons -
1. Wavelength of RED colour is most in the VIBGYOR series. If wavelength is more, it is less scattered.
2. It is least scattered by other particles like fog,smoke. As it is least scattered , less light deviates from its original path. Hence more light reflects back and reaches our eyes. Hence we can see RED colour properly even on a foggy day.
I think the major reason has to do with how light gets absorbed in fog,
particulates, haze, etc.
We know that light is scattered (and thus attenuates or gets weaker) as it
travels through a scattering medium composed of small particles.
As it turns out, red light is scattered (is weakened) less than other
colors. In fact, of the light spectrum, blue is scattered the most and red
red light weakens the least in traveling in the air. That is
why stop signs and other critical lights are red.