An image forming apparatus includes an acquisition unit, a printing unit that performs a printing job, a communication unit, and a control unit. An installed device is an illumination device. Upon determining that a printing document is a first task document, the control unit controls the communication unit to transmit a first color change instruction. Upon determining that a printing document is a second task document, the control unit controls the communication unit to transmit a second color change instruction. The first color change instruction is an instruction for increasing a color temperature of illumination light. The second color change instruction is an instruction for decreasing a color temperature of illumination light.