visible light along with others in the electromagnetic spectrum (gamma rays, x rays, ultra violet, infra red, microwaves and radiowaves) are energy waves..pretty much. Visible light are those colours in the rainbow (red, orange, yellow, green, blue, indigo and violet) and work in that whichever colour or colours are reflected are those colours we "see" eg blue objects absorb all colours EXCEPT blue which is reflected to the eye and the brain tells you you see blue. White is total reflection of ALL the colours, while Black is total absorbtion...and in reality, black is not actually a colour because it absorbs everything and not reflect anything like a colour does. So tying it all together, because the black absorbs all the colours (which are energy waves) these objects heat up because more energy is being absorbed by it, while white things reflect this energy and tend not to heat up in the same way as the energy waves are reflected. If you were going to be more precise blue objects would absorb more energy than red objects because blue/indigo/violet end of the spectrum has more energy in its waves than at the red end.