A display device includes a display, a sensor module which senses a color temperature of light incident to the sensor module from an outside of the display device, and a processor electrically connected to the display and the sensor module. The processor operates in a first mode or a second mode or is turned off, depending on a user input, outputs a moving picture to the display in the first mode, outputs a still image to the display if detecting a user, turns off the display if failing to detect the user, in the second mode, adjusts a color temperature of the still image based on the color temperature sensed by using the sensor module in outputting the still image, and outputs the still image having the adjusted color temperature to the display.