1. An image processing device comprising: a first color detection means for detecting colors of a first image data by each processing unit; a second color detection means for detecting colors of a second image data that serves as the first image data's background by each processing unit; and a color adjusting means for specifying a uniform adjusting color that makes the first image data recognizable against all colors of the second image data that serves as the first image data's background, concerning the first image data that have approximately equal colors.