1. An image processing device that identifies a characteristic of a lip from a face image including a mouth of a person, the image processing device comprising: a representative skin color determination unit that determines a representative color of a skin in the face image; a candidate color determination unit that sets a plurality of regions in the face image such that at least one of the regions contains a part of the lip, and determines representative colors of the regions as candidate colors; and a representative lip color determination unit that determines a representative color of the lip from the plurality of candidate colors, in accordance with a difference in hue and saturation between the representative color of the skin and each candidate color.