designating or of a printing process using separate plates in yellow, red, blue, and black, so as to produce any color or colors
See four-color in American Heritage Dictionary 4
(fôrˈkŭlˈər, fōrˈ-)
adjective
Of or being an overprinting or photographic process in which three primary colors and black are transferred by four different plates or filters to a surface, reproducing the colors of the subject matter.