The subtractive primary colors are Cyan, Yellow and Magenta. These pigments act like small filters, trapping or absorbing some color components and reflecting others. Red, Green and Blue rays are the three-color components of white light. Equal amounts of full intensity Cyan, Magenta and Yellow can be mixed to form a Black color. This is theoretical, in reality the results are not always ideal due to the limitations of the primaries themselves or in the media.
Observed results are usually a dark green or muddy brown in stead of black.
This color combination is often referred to as CMYK or process color. Mixing equal amounts of Cyan and Yellow pigments produces Green pigment. Mixing equal amounts of Magenta and Yellow pigments produces Red pigment. Mixing equal amounts of Cyan and Magenta produces Blue pigment. Varying the combination and pattern of pigments produces all other colors.