Surely the "genetic" of the various color morphs of the aesculapian snakes in not uniformly distributed throughout the wide areal of this species.
For example, in Cres, the majority of aesculapian snakes I've seen were the melanistic ones.
I could say, every 20 aesculapian in Cres, 12 were melanistic, 6 typically uniformly brown, and 2 faint striped.
By me near Pavia (northern Italy) I've found in 50 years of observations only one melanistic specimen (I've pictures of this one), and the other specimens were approximately 50% uniform brown and 50% faintly striped, with rare observations of some exceptionally well striped individuals. This in a total of probably more than one hundred specimens observed!
In the pictures taken from the religious processions of central Italy (in Pretoro only aesculapians are captured, and no Elaphe quatuorlineata, whereas in Cocullo mainly Elaphe quatuorlineata with some longissimus as side dish
), as I said, I've never seen faintly striped individuals. Not to speak about well striped ones!