a traffic signal head uses a plurality of led light sources mounted in one or more containment volumes in a housing . one version uses identical three - color led light sources distributed through the containment volume : each source having a red light generating element , a yellow light generating element , and a green light generating element . a second version uses identical two - color led light sources distributed through the containment volume , each source having a red led light generating element and a green led light generating element . for the second version , activation circuitry enables individual activation of the red led elements to produce red signals , individual activation of the green led elements to produce green signals , and concurrent activation of both types of led elements to produce yellow signals . both versions can be electrically configured to display any of the three colors , as well as special symbols - such as directional arrows .