The red, blue, green, and yellow crystals are for questing in Un'goro. (With use for the gnome in the back of the jeweled cave in Marshal's Refuge, or the Crystal Pylons.)
They cannot be used in Jewelcrafting. The ONLY other thing those gems come in useful for is getting the Pylon buff crystals, and using them in relation to LIBRAMS.
And considering most of the Outlands gear outranks those old head-slot enchants, it's practically useless now.
No need to save/sell those on the AH. However....Un'goro soil still goes well. Sell/save that if you want to, so people can rep up with Darnassus or Cenarion.
