Subtractive Colour Mixing (inks) CMYK
Subtractive colour mixing: printing inks (cyan, magenta, and yellow) are shown pouring from cans onto a sheet of paper. The filtering effect of each one of these inks creates all the colours necessary for colour printing. In real four colour printing the inks are applied as screens (tiny dots that vary in size to carry the image information). Black ink is also used to enhance contrast and give an outline to the colours.
CYAN subtracts RED passes BLUE & GREEN
MAGENTA subtracts GREEN passes RED & BLUE
YELLOW subtracts BLUE passes RED & GREEN