That render is just fine I think - it gets the light from correct angle. It just doesn't fits in colors. If you done the render I'd suggest multiple light-sources, a green and a yellow. If you didn't than similar can be done in PS by playing with levels (adjustment).
I'll paly with the rubberband too. :$
EDIT: Contrast made it a lot better yeah, still the colors.
EDIT2: Or alternatively, you can put the colored space-background behind it with a layer-mask (so the only visible what's directly covered by the render layer) and try different blending mode-opacity combinations. That's what I did with an uniform-gray whale a couple posts before.