A method of color conversion from a red-green-blue (RGB) color space to a red-green-blue-white (RGBW) color space on an input image includes calculating RGB and white gains with respect to an image block of the input image, calculating RGB and white gain with respect to a pixel of the image block, wherein the white gain with respect to the pixel of the image block is adjusted based on the RGB gain with respect to the pixel of the image block, and performing the RGB to RGBW color conversion based on the RGB and white gain with respect to the pixel of the image block, which improves local color and detail performance of an output image corresponding to the input image.