1. A method of color image forming, comprising: providing a plurality of detachable image forming mechanisms for forming color images, each said image forming mechanism individually using a color toner different from each other, and an image carrying member for carrying said color images sequentially overlaid into a single color image; detecting an individual exchange of one of said plurality of detachable image forming mechanisms; and performing an adjustment for eliminating displacements of color images formed by said plurality of detachable image forming mechanisms, in accordance with a detection of said individual exchange of one of said plurality of detachable image forming mechanisms detected in said detecting.