1. A method of calculating a color value, comprising: a generating step of generating image data used for printing a color chart having a plurality of color patches with a printing machine, color values and positions of the color patches being associated with each other; a displaying step of displaying an image simulating the positions of the color patches on the color chart; an indicating step of indicating, on the displayed image, a coordinate corresponding to the position of a color that has been selected as a color that is closest to a designated color to be reproduced, from the color patches of the color chart in response to a predetermined command operation; and a calculating step of calculating a color value of the color that is closest to the designated color based on the color values and positions that are associated with each other and the indicated coordinate, wherein, in the generating step, the image data is generated such that the color patches are arranged in a two-dimensional pattern around the designated color, and color differences in an equal color space between adjacent ones of the color patches are represented by a substantially equal interval along a row or column of the color patches, and wherein, in the calculating step, the color value of the color that is closest to the designated color is calculated according to an interpolating process or an extrapolating process.