A device for discriminating variations in the magnitudes of color differences. It is composed of an optoelectric conversion device consisting of a CCD facing a sample at a right angle with respect to the optical axis of the CCD. The can be moved by stepping motors along the X and Y coodinates on the plane on which the sample is mounted. The stepping motors are controlled by an 8-bit personal computer. Rods are used to move the CCD. The variations in the magnitudes of the color differences are sensed at certain X and Y positions in finite time intervals. A Xenon lamp is used as a light source to illuminate the sample. The system of discriminating variations of the magnitudes of color differences consists of a CCD image, a 16-bit personal computer, an AD converter, and a CRT. The discrimination is carried out by using subjective equivalent hue data and functional data on the personal computer. The former is given by the upper and lower limits to the subjective equivalent hue with respect to the standard stimuli at a certain wavelength in the visible range to standard eyes having a specific color sensation. The latter is obtained from the spectral response of the optoelectric conversion device, i.e., the CCD imager.