Red, green and blue densities of a color negative are measured at a plurality of points thereon. The measured densities are normalized by a normalizing circuit so that the same levels of density signals can be obtained regardless of the gamma value and sensitivity of the negatives when the same subject matter is photographed under the same conditions. The normalized density signals are plotted in a chromaticity coordinate system and examined as to whether or not they fall within a given region defining a particular color in the chromaticity coordinate system. When the level of the normalized signals with respect to a given point falls within the given region, the point is determined to have the particular color defined by the region in the chromaticity coordinate system. When the color negative includes a predetermined number of points of the particular color, the exposure in a color printer is controlled to reproduce the particular color in a desirable condition.