The darker it is under the skins, the less that the color of the skins will show. Copperhead skins are some of the "thinnest" skins that you can put on a bow, the best thing to do would be to paint the surface of the limb with something "light colored".
In maineac's picture above, you can see the darker patterns of the zebra wood showing through. While looking unique with the wood pattern showing through, I prefer the look of the pattern on the snakeskins themselves.
I myself, would have a hard time covering up a beautiful piece of wood with "anything" 'cept for a clear finish. The black carbon, on the other hand just isn't attractive to me and in my opinion would look much better with some nice snakeskins on them......painted a lighter color on top of the carbon, of course.
I had a pretty lengthy conversation with Bob Morrison about the very same question that you asked. He's putting some copperhead skins over some black carbon on my Zipper SXT longbow limbs as I type. I should have them sometime in the next week or so.
Winterhawk1960