Suppose printers used red, green and blue ink instead. Which colours would you mix to make yellow? You couldn’t do it. Mixing red and green light gives yellow because you are adding together photons of diff erent wavelengths. But with ink, you start with white ambient light and refl ect it off the pigment molecules, which absorb some of the photons. So you are subtracting wavelengths, rather than adding them. The printer ink colours of cyan, magenta and yellow are used because they each absorb one of the primary colours – yellow ink absorbs blue light, and refl ects red and green, for example.
