A color printer system includes plural data transmitting units that transmits image data of each color to an engine, and a printing control unit that controls the plural data transmitting units. The printing control unit and an image data generating apparatus are connected by a first transmission path, and the plural data transmitting units and the image data generating apparatus are connected by plural of second transmission paths allocated to each color. The image data generating apparatus includes: an image data generating unit that performs bitmap expansion on a print job for each color to generate image data; and a communication unit that sequentially allocates the image data of colors other than a color not used for the superimposed printing to the second transmission path, which is allocated to transmit the image data of the not used color, and transmits the image data in units of transmission.