Modification of color values in a page description file can be carried out by converting implicit color commands within the page description file to explicit color commands. The color values specified by the explicit color commands within the page description file then are adjusted to calibrate an output device for enhanced color fidelity. Implicit color commands specify color values indirectly, for example, by defining color as a function of other graphic information and color reference values. Consequently, color modification prior to RIP conversion generally is difficult. Conversion and modification of explicit color values provides a higher degree of color conversion accuracy without the need for RIP conversion of the page description file.