Restriction information on a total colorant amount for a medium is obtained. Patches at grid points in a color space corresponding to a plurality of colorants at which the total colorant amount falls within a restriction represented by the restriction information, and a patch at a point surrounded by the patches are generated. Color values are obtained by measuring the colors of the patches printed on the medium. It is determined based on a color prediction value between the grid points whether the measured color values are appropriate, and if so, a color value at a grid point at which the total colorant amount exceeds the restriction is estimated based on the measured color values. A color separation table is created based on the measured color values and the estimated value.