Why do the primary colors make white? Why do the primary pigments make black?
In the first case it is additive mixing of light sources. If you take three primary colors RGB and turn them on full intensity to the same spot, then you have white light. It’s the reverse of splitting the white light into the colors of the rainbow. In the second case it is absorption of colors. The objects that are pigmented are hit by white light. Some colors are absorbed others remain as apparent colors. Red pigmented paint absorbs mainly the green and cyan colors. Yellow paint absorbs mainly the blue and purple colors. Blue paint absorbs mainly the yellow and orange colors. When you mix several of those pigments most of the colors are absorbed and the result is black = no reflected color.
