This LED Wristwatch project is a pattern based on distribution of different colored LEDs. The time is shown through the number of LEDs in each color mode. As the picture is displaying the time 3:45pm (1 red, 5 yellow, 4 green, 5 blue - 15:45 or 3:45pm)

Since it involves special programming methods and SMD components thus, it asks for meticulous electronic hobbyists.
it is a way of controlling lots of LEDs with only a few pins by taking advantage of the tri-state nature of a microcontrollers pins and the forward voltage of the LEDs.
Thanks: rgbphil
Via: makezine