Ohh, a needler... always wanted to make one of those, thought it'd be a fun build. And it looks like its going to be for you. About your small issue though, (and this could be the lack of sleep talking), but couldn't you put a *base* of some sort of desired colored LED's under the clear casted needles? 1 per needle is all it would take, I would think, unless you don't think that would give the desired effect. Anyway, whatever you decide to do, can't wait.
The needles. They will be the pièce de résistance! How about just soft/fine sanding the surfaces of the clear resin casts, so they become frosted. Then you can throw LEDs inside (via a drilled channel). The "frosted" surface should "grab" the light. That's an option. But, it'll compromise on the clear crystal look.
I'm thinking Superman's Fortress of Solitude. You know, his little control panel when he activates it. That could be a reference.