Multi-colored diodes?

I recently noticed a small eletronic message board. It uses three colors in its messages, and any one spot on the message board could take on any of the three colors at any one time. How is this possible? - Jinx

Like this.

There are probably 2 LEDs in each T-1 or T-1 3/4 package, with three leads: a common anode (or cathode) and 1 lead each for the remaining cathode (anode) for each LED. One LED on is one color, the second LED on is another color, and both on mixes to make a third color.

I think it’s wrong to judge an LED by the color it emits.