An image color enhancement method for a display comprises the steps of: gathering tristimulus values of CIE1931 color space in light of all RGB combination of an image shown on the display, and computing a relative chrominance value and a relative luminance value; obtaining a RGB triangle of color gamut of the display according to the chrominance value; for a chromaticity point D1 which is relative to the RGB triangle of a RGB data, defining a relative saturation is S ⁢ ⁢ 1 = OD 1 OD ; adopting a gain function to conduct gain computing for the relative saturation S1 and obtaining a gain saturation S2; according to a formula OD2=OD*S2, obtaining the gain saturation S2 relative to the chrominance point D2 in the RGB triangle and the chrominance point D2 is located in the line OD; computing the RGB data corresponding to the chrominance point D2 and obtaining the RGB data after saturation enhancement. An image color enhancement device is for executing the image color enhancement method.