(modifier) (of a print or photographic process) using the principle in which four colours (magenta, cyan, yellow, and black) are used in combination to produce almost any other colour
Why Do Brits And Americans Spell Words Differently?Brits and Americans may share a mother tongue, but when it comes to spelling a handful of common terms, we just can't seem to settle on a shared favorite—or is it favourite?—approach.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for four-colour
Occasionally three and four-colour machines are used, but the one-colour type is probably the most common.The Jute Industry: From Seed to Finished Cloth|T. Woodhouse and P. Kilgour