1. A method comprising: receiving a request to perform color conversion during rasterization of a print job object at a printer; determining if a substitution mapping file is available for an output color space to be generated by the color conversion; determining if the substitution mapping file includes a substitution entry for an input color space color value to the output color space in use; generating an output color by using the substitution mapping file to map an input color from an input color space to an output color space if the substitution entry is available; and generating the output color by using a color management system to map the input color from the input color space to the output color space if the substitution entry is not available.