A color conversion section for an imaging device carries out conversion to imaging data imaged by each medical imaging device for eliminating differences in color property of each imaging device, and generates standard color graphic data. To this standard color graphic data, a color conversion section for highlighting a specific tissue carries out color conversion for highlighting a designated specific biotissue, such as a blood vessel, to generate specific tissue highlighted graphic data. To this specific tissue highlighted graphic data, a color conversion section for a monitor carries out conversion for eliminating differences in color property of each monitor to generate display data. Color monitors display graphics based on this display data.