1. A color adjustment apparatus comprising: a color value acquisition unit configured to acquire a color value for a specified paper of a desired image forming apparatus and a color value for one or more types of unspecified paper; a relational expression generation unit configured to obtain, for each of one or more pieces of the unspecified paper, a relational expression associating the color value for the specified paper with the color value for the respective unspecified paper, wherein the relational expression generation unit is further configured to obtain a relational expression based on a predetermined regression learning process with respect to each of the one or more pieces of the unspecified paper, and wherein the predetermined regression learning process is based on the color value for the specified paper and the color value for the respective unspecified paper; a paper information registration unit configured to obtain property information of a reference color for each of the one or more pieces of the unspecified paper and register an association between the relational expression and the property information of the reference color for each of the one or more pieces of the unspecified paper, wherein property information of a particular unspecified paper includes a spectral reflectivity corresponding to a predetermined wavelength of the particular unspecified paper; a predicted color value calculation unit configured to calculate a predicted color value for the specified paper of another image forming apparatus based on the relational expression identified using property information of a reference color for arbitrary paper and a color value for the arbitrary paper of the other image forming apparatus; and a reproduced color value setting unit configured to set the predicted color value as a color value to be reproduced by the desired image forming apparatus.