In the above-described example, if the spectral reflectances of the above-described eleven gradation values are known regarding the reference color, then using eleven second relational equations represented by lines (curves or straight lines) denoted by reference symbols G(z) (z is values in increments of 0.1 from 0 to 1) in FIG. 12, spectral reflectances of eleven gradation values (prediction target gradation values) for the prediction target color are predicted. Note that it is assumed that the spectral reflectances are normalized with the spectral reflectances of the minimum gradation value being taken as 1. In an example illustrated in FIG. 12, the spectral reflectances of the maximum gradation value and the spectral reflectances of the minimum gradation value serve as references. Therefore, when the spectral reflectances for the prediction target color are predicted using the second relational equation based on the characteristics of the reference color, such an error between the prediction values and the actual measurement values is 0 for each of the maximum gradation value and the minimum gradation value. However, the characteristics of the reference color and the characteristics of the prediction target color do not completely coincide with each other, and accordingly, an error occurs between the prediction values and the actual measurement values for the spectral reflectances of the characteristics-acquired gradation value. Accordingly, in the present embodiment, as will be described later, the spectral reflectances of the characteristics-acquired gradation value are included in the reference when creating the second relational equation.

<2.2 Configuration and Spectral Reflectances Prediction Method (Spectral Characteristics Prediction Method)>