Looks like a melanistic animal. This morph is seen quite "common" in a sense that I have seen quite a few pictures of these. They seem to be known from several places and are also bred (cf. http://www.elaphe.info/content/arten/longissimus.php).
Nice find none the less! 

No it's not the black one like this:

it was a gray-blue color, it was very strange and beautiful. I'll send another photo asap to see what I mean 

Okay, I see - I was unsure whether you mean the blue at the neck or the overall coloration. Imho, the blueish may be a result of a fresh shed or a shed that will occur very soon (like the next 2-3 days). I recognized different tints from blue to muddy black and brown also in H. gemonensis var. carbonarius.
I hope you took some nice shots since the animal is an absolute beauty. 

Wow, beautiful animal Illias! 

another one from another pov