An electronic device may include a display having an array of display pixels. Each display pixel may include a red subpixel, a green subpixel, a blue subpixel, and a white subpixel. The display may be controlled using display control circuitry. The display control circuitry may convert frames of display data from a red-green-blue (RGB) color space to a red-green-blue-white (RGBW) color space. The display control circuitry may supply data signals corresponding to a frame of display data in the RGBW color space to the array of display pixels. A frame of display data may be converted from the RGB color space to the RGBW color space based on an amount of color saturation in the frame of display data, based on information identifying what code is running on control circuitry in the electronic device, and/or based on ambient lighting condition information.