A display device and a driving method thereof includes categorizing red-color, green-color, and blue-color image signals as belonging to one of first and second signal regions, detecting if the image signals have more signals belonging to the first signal region than the second signal region or if the image signals have more signals belonging to the second signal region than the first signal region, driving an image display portion in a first manner if the image signals are detected to have more signals belonging to the first signal region than the second signal region, and driving the image display portion in a second manner if the image signals are detected to have more signals belonging to the second signal region than the first signal region, the image display portion including a plurality of pixels, each of the pixels having red-color, green-color, blue-color, and white-color sub-pixels.