Subtractive colorimetry achieves metameric matching by removing portions of the spectrum from white light. The subtractive counterparts to the additive colour primaries are those which when removed from white leave the red, green, and blue accordingly cyan, magenta, and yellow. Combinations of these subtractive colours in various add mixtures provide metameric matches to many colors. Subtractive colour principles are employed in all hard-copy colour images and in light-valve systems such as colour transparencies, LCD panel display, motion-picture films, etc.