1. Skip forward to the giant battle scene where all the jedi's are fighting in the arena.
2. Right after Yoda comes to save everyone, look for a weird looking Jedi. He has a cone-shaped head and a white beard.
3. Watch him twirl his lightsaber for a brief moment. I believe the color is blue.
4. The camera flashes away for a few seconds.
5. When the camera comes back to him, he has a green lightsaber!