1. A color image processing apparatus comprising: determination means for calculating a ratio of an area of gray color in an input color image data with each value of R, G and B being equal within a predetermined margin of error to an entire area of the input color image data, and determining whether the ratio is greater than a predetermined value; and color adjustment means for adjusting color of the area of gray color such that, when the ratio is greater than the predetermined value, the color of the area of gray color is adjusted to a first point close to an origin in an ab plane in a CIELab color space where a color adjustment is performed, and when the ratio less than a predetermined value, the color of the area of gray color is shifted to a second point by a predetermined value toward the negative direction along the b axis in the ab plane in the CIELab color space, whereby color image data is generated.