Also, cellos made out of wood are usually shades of brown, so I'm not sure what it would actually look like. maybe it switches between a painfully bright neon green to a really horrible shade of brown. Or maybe it's those colors mixed up in a swirl, like marbled paper, or a color that is an even mix of them which is painful to look at and makes you want to barf at the same time. There are lots of possible color combinations.