An image forming apparatus includes: a drum cartridge to which one of a first toner cartridge and a second toner cartridge is attachable; a frame including a first slot and a second slot; and a controller including a control memory and a processor. The drum cartridge to which the one of the first toner cartridge and the second toner cartridges is attached is attachable to one of the first slot and the second slot. The control memory stores first color information allocated to the first slot, and second color information allocated to the second slot. In a state where the drum cartridge is attached to one of the first slot and the second slot and when the drum memory does not store any color information, the processor is configured to perform: writing, into the drum memory, one of the first color information and the second color information which is appropriate.