A method for designating a representative color which is expressed based on a reliability that a representative color of an image region expresses an image region is disclosed. This method includes a step for expressing a reliability of the representative color value as a color information of the image region together with a representative color value which represents the image region in a method using a color value as an information with respect to an image region, for thereby expressing a color information of an image region using a reliability and a color segmentation method of an image region.