An apparatus reduces color fringing in a color image, so that a post-processed color image is positioned in a restricted area in a chromaticity diagram. Where a first line passes a first point corresponding to a target pixel of the pre-processed color image and an origin, the restricted area is located on a side of the origin with respect to a line that is perpendicular to the first line and passes the first point, and held between two parallel lines separated from the first line by an equal distance that is equal to or smaller than half a distance between the origin and the first point. The restricted area is held by two lines each of which passes the origin and represents a boundary between one of the two color components and an area representing a color component made by mixing the one color component and another color component.