Subtractive colour

The subtractive colour theory explains colour mixing with pigments (eg paints and inks). The three primary subtractive colours are yellow, cyan, and magenta. Secondary colours are red-orange (obtained by mixing yellow and magenta), violet (obtained by mixing magenta and cyan), and green (obtained by mixing cyan and yellow). Mixing all primary colours will produce a darkish grey.

(Image embedded from Wikipedia on 2 January 2011)

The subtractive primary colour theory is behind modern printing processes, or the CMYK colour model. The range of primaries is actually extended with black (K) in order to produce deeper tones, and is typically printed on a white background (eg white paper) in order to obtain lighter tones (without the addition of white). In principle, then, we could consider the primary colours to be actually five: cyan, magenta, yellow, black, and white.