I say give us some sort of coloristic "alchemy". I want Cyan crystals, for example. All high-saturated hues should be available. Also, Anakin during battle with Obi-Wan in Episode 3 showed some pretty obvious signs of Sith corruption, harvested from all that slaughter. He used Blue crystal. Maybe it's better to remove all restrictions on crystal colors? If my sith is evil as hell, but he does not care enough about traditions and just prefers green color - he should be able to do it. On the other hand, I sometimes think about dark-side Jedi with red glowsticks, who, perhaps, should be killed on sight by their traditional light-side peers.