Why Danger Signals are Red in Colour ?

🔴 It is all about scattering effect of lights with different colours. Less the scattering causes greater distance of travelling the light. Less scattering is also helps the light to travel through fog, cloud, dust e.t.c.

🔴 The scattering of light is inversely proportional to the fourth power of the wavelenght of the light.

🔴 Red colour has bigger wavelength than any other colour. So the scattering of light is less for red light which leads to traveling of greater distance. Thats why red light is used for danger signal. So that it can be visible from far distance.