At the moment, I do not know of any way for a Republic player to obtain a Purple Color crystal, judging by your avatar you're Empire so you're good there. Also AFAIK there is currently no confirmed drops for Purple Lightsaber schematics so the only way to get one is in either Champion PvP gear or it's equivalent of Columi PvE gear. Perhaps the easiest non-PvP way to get one would be to run the Battle For Ilum Flashpoint on Hard Mode and get the Columi Off-hand weapon token drop from the final boss. Well, if you can find a good group I suppose a normal mode Operation might be easier, but you have to find a group and that'd be the problem there.
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