Oh, yea, it got the name gas gangrene because the bugs actually produce gas as a side effect and the wounds smelled differently than usual gangrene, which pretty much smelled like dead/rotten flesh. The gas gangrene smell is apparently stronger and stays around longer. That's what my mom told me and she'd actually treated some cases when she was young. The color of the skin you're describing matches her description, I believe. She said the skin was a bright green that you wouldn't see with anything else and that it was pretty much uniform.
(This following part is really gross even to me, so if it's not your chicken you may not want to read further.)
She also said that pockets of the gas would form in the tissue, including under the skin and that the skin would turn a bright green to a purplish or greyish green, (she thought) depending on how much jaundice was being caused by the infection. (Jaundice causes the skin to turn yellowish and in combination with the greenish color from the C. perfringens infection itself, was what she thought caused the bright green color. She also said that there would be gas bubbles sometimes right under the skin and that when you pushed on the skin a little it would have a funny, crackly feeling. She also said that the infection would produce dark fluids that looked a lot like dark blood mixed with other fluid. Come to think of it, I think she did say there was a stage were the tissue was darker, more purplish than green, but that (at least with her patients) the skin always turned a very distinctive shade of green.