There is provided a color processing apparatus comprising: a calculation unit configured to calculate, for each of a plurality of light sources, a first colorimetric value that is obtained by measuring a color having a spectral reflectance indicated by spectral reflectance information under the light source; a mapping unit configured to obtain, for each of the plurality of light sources, a second colorimetric value by mapping the first colorimetric value of the light source within a gamut under the light source; a color separation unit configured to obtain the output information from a plurality of the second colorimetric values, by adjusting the output information such that an error between a colorimetric value obtained by measuring a color output by the image output apparatus according to the output information under each of the light sources and the second colorimetric value for the light source is minimized.