With a pixel included in image data as a reference pixel, a pixel that shares the same pixel value as the reference pixel or a pixel similar to the reference pixel is judged as a shared pixel, and for the pixel judged as the shared pixel, color of the reference pixel is regarded as a color judgment result of the shared pixel, thus making it possible to reduce color calculation processing for the shared pixel. This makes it possible to provide a color judging apparatus operating at higher speed and the like. Thereby, it is possible to provide the color judging apparatus operable at high speed and the like by reducing the number of times of the color calculation processing executed for an input image.