Black and White

They are not colours...

Technically speaking, white is not a color at all, but rather the combination of all the colors of the visible light spectrum. When all the wavelengths of the visible light spectrum strike your eye at the same time, white is perceived. Thus, visible light is sometimes referred to as white light. If all the wavelengths of the visible light spectrum give the appearance of white, then none of the wavelengths would lead to the appearance of black.

Once more, black is not actually a color. Technically speaking, black is merely the absence of the wavelengths of the visible light spectrum. So when you are in a room with no lights and everything around you appears black, it means that there are no wavelengths of visible light striking your eye as you sight at the surroundings.