1. An image processing device comprising: a processor; and a memory storing instructions, wherein the instructions cause the processor to: detect at least a part of a region of interest included in an image; set the at least a part of the region of interest as an initial region; detect an expansion region by expanding the initial region; calculate color feature data of the initial region and color feature data of the expansion region; calculate a difference between the color feature data of the initial region and the color feature data of the expansion region; determine to which one of multiple classification items the region of interest belongs based on the difference between the color feature data of the initial region and the color feature data of the expansion region, wherein the multiple classification items include: a region having an area of the region of interest greater than a first predetermined threshold; a region having an area of the region of interest equal to or less than the first predetermined threshold and in which the difference between the color feature data in the region of interest and the color feature data surrounding the region of interest is greater than a second predetermined threshold; and a region having an area of interest equal to or less than the first predetermined threshold and in which the difference between the color feature data in the region of interest and the color feature data surrounding the region of interest is equal to or less than the second predetermined threshold; and determine a check priority of the region of interest based on the one of the multiple classification items to which the region of interest is determined to belong.