Note that, in the example illustrated in the portion B in FIG. 5, the reflectances take minimum values in the vicinity of a wavelength of 560 nm, and reflectances of the same value appear at a wavelength larger than 560 nm and a wavelength smaller than 560 nm. Hence, for example, when the combination data are sequentially plotted on the relational graph in a descending order of the wavelengths, turning-back of a locus thereof occurs. However, as seen from FIG. 7, the relationship between the reflectance of the maximum gradation value and the reflectance of the focused gradation value is unchanged before and after the turning-back. From the above, it is conceivable that, if the sample color and the prediction target color are colors close to each other, the reflectances of the focused gradation value for the prediction target color can be accurately obtained from the reflectances of the maximum gradation value for the prediction target color, using the “relationship between the reflectances of the maximum gradation value and the reflectances of the focused gradation value” for the sample color.
