First, a color close to a prediction target color is selected as a first similar color from among a plurality of similar candidate colors. Next, a first relational expression representing a relationship of spectral reflectances of a solid patch between a reference medium and a prediction target medium is obtained for the first similar color. Then, spectral reflectances of the solid patch in the prediction target medium for the prediction target color are predicted by applying spectral reflectances of a solid patch in the reference medium for the prediction target color to the first relational expression. Finally, spectral reflectances of each halftone patch in the prediction target medium for the prediction target color are predicted based on the prediction result.