I like O'Neille's concept...I remember many an impressive "Candy Apple Green" paint job from custom car show that i used to attend.

I wonder it using a clear material like plexiglass as a base material wouldn't help to give it some of that translucency that would make it look a bit more "alive"...we are led to believe that Kryptonite is kind of a radioactive material that's emitting deadly (to Superman...and eventually to Earth people, as it turns out) rays...it's like it should have a certain inner glowing quality. Some transparent emerald green followed by clar coat to seal it off?

Best

AA