First, the prediction target color is set (Step S100) In the present embodiment, an ink color for which the spectral reflectances of the maximum gradation value, the spectral reflectances of the minimum gradation value, and the spectral reflectances of at least one intermediate gradation value are obtained is set as the prediction target color. In this regard, for example, the process of Step S100 may be achieved in such a manner that a user inputs information on the prediction target color on a predetermined screen, or the process of Step S100 may be achieved in such a manner that the spectral reflectances prediction program 141 reads a data file including information on the prediction target color. Note that, hereinafter, such an intermediate gradation value for which the spectral reflectances are obtained regarding the prediction target color will be referred to as a “characteristics-acquired gradation value.” For example, if spectral reflectances of a gradation value of 0.3 and spectral reflectances of a gradation value of 0.5 are obtained regarding the prediction target color, then 0.3 and 0.5 are such characteristics-acquired gradation values.

Next, for each of the above-mentioned plurality of sample colors, a relational equation that represents a relationship between the spectral reflectances of the maximum gradation value and the spectral reflectances of the characteristics-acquired gradation value (hereinafter, this relational equation will be referred to as a “first relational equation”) is obtained (Step S110). In this Step S110, for each of the sample colors, a number of relational equations equal to the number of the characteristics-acquired gradation values are obtained. When 0.3 and 0.5 are the characteristics-acquired gradation values as in the above-described example, two first relational equations are obtained for each sample color.