Primary colors are the colors of a color model from which all other mixed colors are generated.
Each color model contains three primary colors. In the case of the RGB color model, these are the additive primary colors red, green and blue, and in the CMYK color model, the subtractive primary colors cyan, magenta and yellow.
If you mix two primary colors, you get a secondary color. In both color models mentioned, the secondary color of one color model corresponds to the primary color of the other color model. Example: If you mix the primary colors red and blue additively, you get the secondary color magenta, which is a subtractive primary color in the CMY color model. If you mix three primary colors together, you contain a tertiary color.