coloration and pigment depend on enviornment and diet to some degree.....just like the bass we all chase. grass bass are dark, while muddy water bass are light colored....the head to me looks alot like that of a viper.
my mother's best friend was bitten by a snake in her yard, her husband killed the snake and took a close up picture with a polaroid camera. the doctors treated her for a water moccisan(spelling?) bite based on the picture...she showed no signs of improvement and almost lost her hand from the elbow down. eventually she healed. a year later she went to a snake bite seminar at a hospital in houston. she showed the picture to the "snake bite expert doctor" he told her it was an immature and oddly dark colored copperhead and the hospital treated her for the wrong type of snake.
i'm not claiming to be a snake expert but if a snake has a diamond shape head, i stay away from it, or kill it.
copperheads are not aggresive snakes, they usually will not strike at a human unless provoked, and usually it takes a lot of provocation. whereas water moccisans are very aggresive and will go out of their way to strike at a human.
and by the way, contrary to popular beleif, snakes can bite under water. it happened to a kid when i was in high school, he was swimming in his pond and got bit by a moccisan between the toes. hahaha
just my $.02 worth.