A color processing apparatus for determining grid points for color patches to be printed and measured, the apparatus comprising: inputting means configured to input spectral reflectance data of a plurality of color patches of primary colors of color materials, and a color patch generator, wherein the color patch generator is adapted to a) acquire a number of color patches to be printed as a designated number Nd; b) initially set grid points of tone values for respective color material values; c) form grid point information based on the initially set grid points, wherein the grid point information includes color-material values obtained by sampling those of each color material at given intervals, and it includes a flag indicating whether or not a primary spectral reflectance memory holds spectral reflectance data; d) calculate the color-material values of the respective grid points, and count the number of color patches which are printable within the limitation range of the total amount of applied color materials as a printable number Nc); e) compare the printable number Nc and the designated number Nd, and when Nc < Nd, f) acquire measured spectral reflectance data of the color patches corresponding to the initially set grid points of those of the color patches of the primary colors; g) estimate, based on the data acquired in f), spectral reflectance data of the color patches of the primary colors which are not acquired in f); h) calculate root mean square errors between the measured spectral reflectance data of a plurality of color patches of primary colors of color materials and the spectral reflectance data estimated in g); and i) detect a color material and color-material value corresponding to the maximum calculated root mean square error, and add a tone value corresponding to that color-material value as a grid point of that color material. inputting means configured to input spectral reflectance data of a plurality of color patches of primary colors of color materials, and a color patch generator, wherein the color patch generator is adapted to a) acquire a number of color patches to be printed as a designated number Nd; b) initially set grid points of tone values for respective color material values; c) form grid point information based on the initially set grid points, wherein the grid point information includes color-material values obtained by sampling those of each color material at given intervals, and it includes a flag indicating whether or not a primary spectral reflectance memory holds spectral reflectance data; d) calculate the color-material values of the respective grid points, and count the number of color patches which are printable within the limitation range of the total amount of applied color materials as a printable number Nc); e) compare the printable number Nc and the designated number Nd, and when Nc < Nd, f) acquire measured spectral reflectance data of the color patches corresponding to the initially set grid points of those of the color patches of the primary colors; g) estimate, based on the data acquired in f), spectral reflectance data of the color patches of the primary colors which are not acquired in f); h) calculate root mean square errors between the measured spectral reflectance data of a plurality of color patches of primary colors of color materials and the spectral reflectance data estimated in g); and i) detect a color material and color-material value corresponding to the maximum calculated root mean square error, and add a tone value corresponding to that color-material value as a grid point of that color material. a) acquire a number of color patches to be printed as a designated number Nd; b) initially set grid points of tone values for respective color material values; c) form grid point information based on the initially set grid points, wherein the grid point information includes color-material values obtained by sampling those of each color material at given intervals, and it includes a flag indicating whether or not a primary spectral reflectance memory holds spectral reflectance data; d) calculate the color-material values of the respective grid points, and count the number of color patches which are printable within the limitation range of the total amount of applied color materials as a printable number Nc); e) compare the printable number Nc and the designated number Nd, and when Nc < Nd, f) acquire measured spectral reflectance data of the color patches corresponding to the initially set grid points of those of the color patches of the primary colors; g) estimate, based on the data acquired in f), spectral reflectance data of the color patches of the primary colors which are not acquired in f); h) calculate root mean square errors between the measured spectral reflectance data of a plurality of color patches of primary colors of color materials and the spectral reflectance data estimated in g); and i) detect a color material and color-material value corresponding to the maximum calculated root mean square error, and add a tone value corresponding to that color-material value as a grid point of that color material.