To clarify, it's only in Imperial Columi weapons. Reps have to buy it off the GTN unless they get a drop from the mats box. Purple has never dropped from a world boss.
Hmm, are you sure? Whenever I asked someone about it I have been told it was from the belsavis World Boss. I think we even once did a run for an artifice guy in our guild.
I am a little confused now. Just to make sure, I mean the purple colour crystal, talking about colour and not "quality".