1. A system for selectively enabling a printer to deposit on a sheet primary or black color dots at each of a plurality of pixel locations, to produce a color image, said system comprising; first memory means for holding a color vector for each pixel, respectively, in the color image; second memory means for storing parameters of a dither cell; processor means coupled to said memory means for comparing said dither cell with each color vector, to select a color component to print at the corresponding pixel location, based on said comparison.