From what I have seen in online pedigrees you would have to go back a hundred years to find any game family of blue colored dogs.
The only documented example is in the ped of Tudor's Black Tige who was sired by a dog named Blue Mike that went back to a line of blue dogs.
https://www.apbt.online-pedigrees.com/modules.php?name=Public&file=printPedigree&dog_id=15093 A very good dog historian (IMHO) in the U.K. who goes by Jackal's Old Country blood has researched in and found the last mention of the line was a pure Blue Paul shown in 1880's.
https://jackalsoldcountryblood.com/the-history-of-blue-dogs-in-apbts-and-amstaffs/ This world is all long gone and can only be verified to a point and I don't promote dog fighting or fighting about it online!
