You might have observed many times that on hot and sunny days, while wearing a dark colored shirt and a light colored pant, the upper part of your body feels comparatively warmer than your lower part. So why does this happen ? How in the world can colors make us feel warmer than we are ?
The answer lies in the fact that the frequency ,ν, of different colors is different. Also it is important to know how objects acquire their colors. A red colored object is so colored because it reflects red color while absorbing every other color of white light. Similarly a white object reflects all colors while a black object absorbs all colors and reflects none.
The energy associated with a ray of frequency, ν, is hν where h is Planck’s constant. So a light ray with higher frequency has higher energy than that with lower frequency. In the visible spectra frequency decreases in the order violet, indigo, blue, green, yellow, orange, red. So violet has the highest frequency while red has the lowest. Accordingly violet color has the maximum energy and red has the minimum.
When white light falls on a red colored object, all colors are absorbed except red. From the Law of Conservation of energy (hν) of each color of absorbed light is transferred to the object as heat. Since a red object reflects the ray with lowest frequency and thus lowest energy, it absorbs a high amount of energy (heat) from the absorbed colors and thus becomes very hot. A black object absorbs all colors of the visible spectra and thus absorbs the maximum amount of heat energy. Thus black is considered the warmest color. A white object reflects all colors and thus absorbs almost no heat energy. So white is the coolest color.