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Why do cyan, magenta, and yellow work as primary colours for colour printing?

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A circular RYB color wheel divided into twelve segments, showing a progression of colors from red, orange, and yellow to green, blue, and violet. — colour The RYB color model is being illustrated on a color wheel.

Cyan, magenta, and yellow are used as primary colours for printing because they function through subtractive colour mixing. Unlike additive systems (like digital screens) that combine light, printing involves colorants—such as inks or dyes—that absorb and selectively reflect specific parts of the visible spectrum.12

To achieve the widest possible range of colours (the greatest gamut) in subtractive processes, the primary colours must be chosen based on their ability to absorb the additive primaries (red, green, and blue). They function as follows:2

Cyan acts as a red-absorbing filter.12
Magenta acts as a green-absorbing filter.12
Yellow acts as a blue-absorbing filter.12

By mixing these pigments in varying amounts, printers can subtract specific wavelengths from white light to produce a vast spectrum of hues. While the RYB (red, yellow, blue) model is often taught in art contexts, the CMY model is scientifically superior for colour reproduction because it provides a significantly larger range of achievable colour mixtures. In practice, black is also added to this model—forming the CMYK system—to improve contrast and depth.123