Please be more precise. As already mentioned, the dynamo doesn't involve LEDs or any kind of control. It's just an AC generator. The on-off switch, rectifier, current regulator are usually are usually inside the front light.
You can think about a front light using colored LEDs, consider however that the design must comply with official regulations. I guess colored front lights, or back light colors other than red won't be permitted.
Using my vast technical expertise on the subject:
Prashantakerkar: You need a green dynamo to generate the green electricity for the green LED, A blue dynamo to generate blue electricity for the blue LED, a yellow dynamo to generate yellow electricity for the yellow LED and a red dynamo to generate red electricity for the red LED. The white one needs lots of dynamos so you can mix the colors to obtain white.