How would I go about constructing this circuit?

I want to build a circuit with three LED's: a red, a green, and a blue. The forward voltage is about 3.5 for the green and blue LED's and 2.0 for the Red. I want it to cycle through the three LED's as such: R -> RG -> G -> GB -> B -> BR -> R indefinitely. Does anyone know how to make this possible? It needs to be battery operated. THANKS!!!!!!