In physics, a color is visible light with a specific wavelength. Black and white are not colors because they do not have specific wavelengths. Instead, white light contains all wavelengths of visible light. Black, on the other hand, is the absence of visible light.
Some consider white to be a color, because white light comprises all hues on the visible light spectrum. And many do consider black to be a color, because you combine other pigments to create it on paper. But in a technical sense, black and white are not colors, they're shades. They augment colors.
