First, a description will be given of the case in which the number of characteristics-acquired gradation values is two. Herein, we focus on a case in which “eleven gradation values in increments of 0.1 from the minimum gradation value (gradation value of 0) to the maximum gradation value (gradation value of 1) are prediction target gradation values, spectral reflectances of these eleven gradation values are obtained regarding a reference color, and a gradation value of 0.3 and a gradation value of 0.5 are characteristics-acquired gradation values.” For this case, the second relational equations are obtained as follows in Step S150. For example, an equation that represents a relationship between the spectral reflectances of the gradation value of 1 and the spectral reflectances of the gradation value of 0.7 with the spectral reflectances of the gradation value of 1 being taken as the first reference and with the spectral reflectances of the gradation value of 0.5 being taken as the second reference is obtained as a second relational equation for obtaining the spectral reflectances of the gradation value of 0.7 for the prediction target color. Moreover, for example, an equation that represents a relationship between the spectral reflectances the gradation value of 0.5 and spectral reflectances of a gradation value of 0.4 with the spectral reflectances of the gradation value of 0.5 being taken as the first reference and with the spectral reflectances of the gradation value of 0.3 being taken as the second reference is obtained as a second relational equation for obtaining the spectral reflectances of the gradation value of 0.4 for the prediction target color. Moreover, for example, an equation that represents a relationship between the spectral reflectances of the gradation value of 0.3 and spectral reflectances of a gradation value of 0.1 with the spectral reflectances of the gradation value of 0.3 being taken as the first reference and with the spectral reflectances of the gradation value of 0 being taken as the second reference is obtained as a second relational equation for obtaining the spectral reflectances of the gradation value of 0.1 for the prediction target color.