In a backlight module of a display device, a first light source, a second light source, and a third light source are respectively and sequentially in a first sub-frame period, a second sub-frame period, and a third sub-frame period of a frame period so that the backlight module emits predominantly the first color light, the second color light, and the third color light during the first sub-frame period, the second sub-frame period, and the third sub-frame period, respectively. At least one of the second and third light sources also emits the second or third color light during a part of the first sub-frame period.