A writing device includes a writing pen and a light emitting diode display panel. The writing pen emits three different-colored optical signals. The light emitting diode display panel includes a control module and a plurality of pixels. Each pixel includes first, second and third light sources, first, second and third light sensing elements, and a touch element. The first to third light sensing elements are configured to receive the three optical signals and generate first, second and third selective signals, respectively. The touch element generates a control signal when touched by the writing pen. According to the three selective signals and the control signal, the control module selectively turns on the first light source, the second light source, and the third light source.