Abstract: A color database, in which a mutual correlation is established among an L*a*b*-color-system L*a*b* value as an attribute with respect to a color stimulus, an RGB value, and a sphere radius which is proportional to a color difference and is set in advance as a value indicating a level at that a person can sensuously distinguish between colors, the sphere radius being a radius of a color sphere having the L*a*b* value as a center point in an L*a*b*-color-system color solid, is included, and when the L*a*b* value or RGB value is input to an input unit, display data generation unit refers to the color database to generate display data in which the color sphere having a center point of the L*a*b* value or the L*a*b* value correlated with RGB value is disposed in the L*a*b*-color-system color solid of a line drawing, the color sphere having the correlated sphere radius.