A method separates a color vector into a colorant vector for a printing system that uses more than four colorants, for example cyan, magenta, yellow, black, orange and green colorants. According to the method, the separation process is split up into partial four colorant processes that contain opponent colors. For example, a first partial process is a cyan, magenta, yellow and black process; a second one is an orange, magenta, yellow and black process; and a third one is a cyan, green, yellow and black process. Continuity of magnitudes of the colorants is achieved across the boundaries of the color gamuts of the partial processes by imposing specific constraints on the combinations of colorants to render a given color. A computer implemented system and a print system are based on the method.