1. An image generating apparatus, comprising: a diagnosis image generating section that generates, as a diagnosis image for every first time interval, at least one of a moving image in which a predetermined part of a human body or an animal is photographed and temporally continuous images based on said moving image; an image target setting section that acquires, for said diagnosis image, a first image at a predetermined time and a second image after a second time interval longer than said first time interval from said predetermined time; a pixel color converting portion that converts, of pixels of said first image and said second image, colors of pixels satisfying a predetermined condition to be distinguishable; and a display image generating section that generates an image for display using said first image and said second image whose colors of the pixels have been converted by said pixel color converting portion.