If you cross a Lacy and a Black Mouth you will get a cross bred and thats all it will ever be. Blue is a dilute of black and I have seen blue pups out of a family of Black mouths when a B&T from that family was bred to a yellow dog from that same family. Blue has allways shown up in cur dogs, the Lacy's dang sure didn't invent it.
BINGO........
As Big O pointed out the "blue" color Is actually a black dog with a modifying gene that dulites the Black color to Blue. That "Blue" color is present in quite a few cur dogs out there. Not Just Lacys. In my opinion is a sure sign of inbreeding, but thats just me.
Waylon