Match the light in your surroundings. The 4.5K Retina display on the 24-inch iMac and the 5K Retina display on the 27-inch iMac have True Tone capability. True Tone technology automatically adjusts the color of the display to match the light in your environment for a more natural viewing experience. Turn True Tone on or off in the Displays pane of Using a Retina display.