An image recording system including a host control unit for supplying image data representative of the images to be printed on a record medium and a printer apparatus for forming printed images on the record medium on the basis of the data received from the host control unit, wherein the printer apparatus comprises an image transfer drum having a photoconductive surface, two or more image developing units responsive to the image data for forming a page of electrostatic latent images on the photoconductive surface, change-over means operative to selectively activate any of the image developing unit into operation, electrostatic chargers and charge erasers for transferring the page of electrostatic latent images on the photoconductive surface to the record medium, characterized in that the host control unit is operative to further supply control data predominant over the modes and conditions in which the images are to be printed on the record medium, the control data containing color data specifying a color or colors in which printed images are to be formed on the record medium and in that, when one of the image developing unit is in operation forming a page of electrostatic latent images on the photoconductive surface, the change-over means activates another image developing unit into operation and de-activates the former.