Most of the leopard hounds (like Plott hounds) are open on track, will get deep, neither one of those things are cur traits. Some of the bigger blockier ones undoubtedly have catahoula in them. The fast, competition type that won hunts and made them popular are basically indistinguishable from a July hound, but a lot of July hounds won't tree, so they probably have a little something added.

July's come merle (leopard), black and tan, high tan, tri-color, buckskin, lemon and white, and have seen brindle. Nobody ever worried about what color they were, unlike the coonhound breeds that came in all colors up until recently. Plenty of July hounds still around, but the Calhoun hound is gone. Calhoun was a foxhound (there were not many coonhounds over a hundred years ago, coon hunting is a recent development in most places)They came solid black. They were common in western North Carolina and Western Tennessee at the time Plotts were becoming a breed from the foundation stock of Hanoverian Hounds from Germany brought over with the Plott family. They might have kept them pure, but other people crossed them on what they had, and what everybody had was foxhounds. Kansas City Heat and Camo Jug moved like they had foxhound in them. There are lots of rumors about big competition winners having a fresh dose of foxhound in them. It gives them a lot of drive.