When you look at it, how large could the range of a copperhead be? If it is heritable, than it makes sense that there may be other snakes that carry the trait in close proximity.

When I was a kid I lived in a rural part of Michigan. There was one pond that had blue colored Green frogs. Not all of them were blue, but I found a quite few there. It was a condition where the frogs lacked the yellow pigmentation as part of their makeup. Thus, they were blue. But I only found them around that particular pond.

If you are experienced or feel comfortable enough with a venomous snake, it may be worth dinkering with.