An image forming apparatus has an input portion that receives original image data, a control portion that generates output image data based on the original image data, a printing portion that performs printing based on the output image data, and a storage portion. The storage portion stores associated color information that defines colors associated with a plurality of prescribed processes respectively. When generating the output image data, the control portion, if the original image data includes a marked region, performs, out of the plurality of processes, the process associated with the color of the marked region.