The confusion around blue Cane Corsos actually stems from the breed standards themselves. Rather than calling dogs that have a diluted black coat blue, the standards call them gray. So yes, blue Cane Corsos exist but they're actually referred to as gray. Bearing that in mind, you shouldn't be paying more for a puppy that's described as blue. Some questionable breeders might try to convince you that blue is rarer/more unique.