Marvel: Dichromatimorphic Skin

Joshua Foley (Elixir)
After Elixir used his mutant powers to heal himself, his skin turned a golden color. This is possibly due to Elixir activating a Secondary Mutation in himself. Elixir's skin normally remains golden, but if he uses his powers to damage to kill his skin turns a deep metallic black. This appears to be a completely involuntary reaction, and it has been stated that Elixir has a hard time converting from black to golden.