1. A method for displaying a result of area extraction processing of dividing a target image into a foreground area and a background area, the method for displaying an area extraction result comprising: a result acquisition step of acquiring a result of the area extraction processing on the target image; an extraction result image generation step of acquiring an extraction result image representing an estimated foreground area or an estimated background area estimated by the area extraction processing or a boundary between the estimated foreground area and the estimated background area, based on the acquired result; and a display step of generating a composite image by combining the extraction result image with the target image, and displaying the composite image on a display device, wherein the extraction result image generation step comprises: a color extraction step of extracting a plurality of colors, which are all or representative colors, from a pixel group in a boundary peripheral area including the boundary between the estimated foreground area and the estimated background area, and disposed on both the estimated foreground area and the estimated background area; and a color determination step of determining a color of the extraction result image so as to be as different as possible from each of the plurality of colors extracted in the color extraction step.