It's funny I cannot answer this question, but I really don't have a very good physical intuition for how color works.
I know that sunlight and (say) light from lightbulb is a superposition of all colors of the EM spectrum. When I pass this "light" into a prism, the longer wavelengths are separated from the shorter wavelengths, resulting in a rainbow.
However, I learned that if something is red, it is absorbing all/most colors except red. Our eyes are seeing the wavelength of red reflected from (say) a red shirt, which is cotton with red dye. So, this red dye is "reflecting" red light, and "absorbing" everything else.
The color black absorbs most colors, while white reflects most colors.
What is going on here physically? When I say "absorb" and "reflect", what does that actually mean in terms of electromagnetism?