Milk appears white because it reflects all light wavelengths. If it were to do absorb all light wavelengths and reflect nothing back, then it would appear black. Milk is primarily water, which absorbs the light wavelengths; but it also has other components: fat, protein, lactose, minerals and vitamins. The fat and protein molecules in the milk reflect the light back, giving it the white colour. If some of the fat from the milk (like in skimmed milk) was removed, it would give the milk a different colour because of the wavelengths the light is reflecting back to our eyes.
Why is milk white?
