Primary colors, for humans, are sets of three colors that can be combined to make a whole gamut of colors. For additive combination of colors, as in overlapping projected lights or in CRT displays, the primary colors normally used are red, green, and blue. For subtractive combination of colors, as in mixing of pigments or dyes, such as in printing, the primaries normally used are magenta, cyan, and yellow.
These choices of primary colors are not unique; early color photography such as autochromes used orange, green, and violet primaries.