I know a few ways. first, you could wait until you get to malachor V and next to the bridge thing there is one. second, you need to talk to greedo after you talk to oondar and stabilize onderon and dantione, then she will have a silver crystal. Lastly, I just reliezed today. in the secret tomb on korriban, save before fighting the vision of revan. then, after you defeat him and get done talking to kriea, you will get some exp, journal entry, and a lightsaber. check the saber in your inventory and see what color it is. if it's not silver, reload and try agian. i got a couple of yellows, a purple, than a silver.