A display device includes a display panel and a panel driver configured to drive the display panel. The panel driver receives input image data corresponding to first, second, and third colors at an input frame frequency, and detects whether the input image data represent a still or dynamic image. If the input image data represent the dynamic image, the panel driver drives the display panel at a first output frame frequency substantially the same as the input frame frequency. If the input image data represent the still image, the panel driver calculates a plurality of flicker indexes of the still image for at least two of the first, second, third colors, one or more combinations of the first, second, and third colors, and drives the display panel at a second output frame frequency that is determined based on the plurality of flicker indexes.