To my knowledge, there is no way that a non-level 50 character can get a Cyan or Purple color crystal. I could be wrong. Orange crystals I believe can come from sabers brought with credits, planet commendations, or dropped from flashpoints. As far as double colored crystals for non-50's go, you can get a Pink-Purple crystal from either Cartel Packs or now the GTN. I believe that there may be some mid game Black-Green crystals on the GTN, but those are hard to come by and can be expensive.