[jQuery] rotate/loop using jquery

here is my problem:

$("#btnTraffic").click(function(){
   $("#trafficLight").css("background-color","yellow");

});

btnTraffic is my button, when I click it, it changes from red to
yellow because of the css.

I want to click it multiple times and have it rotate between red,
yellow and green.

so it starts red, I click it, it turns yellow, then I click it and it
turns green, then click again back to red, so on and so forth. anyone
have any idea how to make that happen? I can change it once no
problem, but I need some type of loop command or something like that.



Thanks in advance !

Glen