History of Blue French Bulldogs

Blue French Bulldogs are a relatively new color variation of the French Bulldog breed. The breed itself originated in France in the 1800s by breeding toy versions of the English Bulldog. Here, they were believed to have been bred with Terriers and Pugs, giving them their bat ears. 

French Bulldogs were bred specifically to be companion dogs and were popular among the French bourgeoisie. The genes responsible for the bluish-gray hue in Blue Frenchies have always existed naturally in the breed. 

Source:

https://pawsafe.com/blogs/dog-breeds/blue-french-bulldog