Subtractive colour mixing

Yellow, magenta, and cyan inks overlap to create the subtractive secondary colours (red, green, and blue). Where all three inks overlap the result is black. This type of colour mixing (using pigments) is the basis for colour printing. However, they generally also use black ink (the K in CMYK) since it is more efficient than relying on the three basic inks. This is known as four colour printing.