A color image forming apparatus provides the prolonged life of the photosensitive drums, carrier belt, and toner of the respective colors and improves the quality of the printed color image. A carrier belt transports a recording medium placed thereon so that the recording medium passes through a plurality of printing mechanisms which print images of different colors on the recording medium in superposition. Each printing mechanism prints an image of a corresponding color. The printing mechanism is adapted to be moved into its operative position where the photosensitive drum of the printing mechanism is in contact with the carrier belt to print the image on the recording medium, and into its non-operative position where the photosensitive drum of the printing mechanism is not in contact with the carrier belt. A controller receives print data from a host device such as a personal computer and checks each page of the print data to determine whether any one of a predetermined plurality of colors is missing in the page. If a particular color is missing in the print data, then the controller outputs an UP signal to a positioning mechanism for a corresponding printing mechanism. If the color is not missing, then the controller outputs a DOWN signal. The printing mechanism moves a corresponding printing mechanism into the operative position if the UP signal is received from the controller and into its operative position if the DOWN signal is received.