PURPOSE: To enable the comparison of a color reproducing range by display common to a CRT and a printer device to handle uniform color space by displaying the cross section of a color solid.

CONSTITUTION: When a lightness index L* and the presence of the display outside a color area are designated (step S101), a minimum value is set to color quality indexes a* and b* (step S102), and whether the display is the one outside the color area or not is judged (step S103), and in the case that the display outside the color area is not to be executed, it is judged whether the present coordinates (L*, a*, b*) in the color space are inside or on the color area or not (step S104), and if the present coordinates are located inside or on the color area, a unit rectangle (Δa*×Δb*) consisting of a single color to be determined by the present coordinates is displayed at the position of the present coordinates (step S109). If the present coordinates are located inside the color area, the display of the unit rectangle is skipped. The cross section of the color solid is displayed by repeating the display of the unit rectangle while increasing the color quality indexes a* and b* to a maximum value by every Δa* and Δb* portion.