To create a color conversion definition defining an association between a color in an arbitrary gamut and a color in a color in a target gamut, there are provided a definition creating step of creating a first color conversion defining an association between a color in a reference gamut close to the arbitrary gamut and a color in the arbitrary, and a definition combination step of combining a second color conversion definition created beforehand defining an association between a color in the reference gamut and a color in the target gamut, with the first color conversion definition created in said definition creating step.