Well only one side of the cube of meat would be the skin side,green with scales; the other sides would be a cooked steak color. By rotating the various cubes on the kabob you will create contrast and make it look realistic.
The steak side should be grey/brownish with some possible black grill marks.
The scale skin side would be dark green, I'd put a little black around the edges as if the skin was getting crispy, and maybe even curled up a little. I'd airbrush the scales on very lightly, using an even darker green.
If you want to make it look fresh you are going to want to finish with a clear glossy wet on the meat sides, like it was juicy and just came off the fire.
And on a personal note, fallout rocks! I have a very cool glowing fallout display in my house with just about all the original stuff I think they made to promote the game including some of the more rare items like the Simtek 1000, a real bottle of Nuka Cola, and the rarest being the Gecko in a Can used to promote Fallout 2.