If your mare is not gray, and the sire is gray, you have a 50/50 chance of a gray (if stallion is hetrozygous. If he’s homozygous you’ll have 100% gray. Cunningham has had non-gray foals, so he’s definitely hetro).
The Balou du Rouet horses have big steps and big jumps and there are several of them standing in the US. (all are bay)
Cunningham is lovely! I seriously considered him for my Riverman mare, but since she’s also gray, I had a 75% chance of ending up with one. I went with a bay stud to reduce my gray chances to 50%, but still ended up with a gray colt 
Gray horses are more work, but they look stunning when all cleaned up. And remember the young gray horses are steel or dappled, and therefore pretty easy to keep clean on a day-to-day basis. It’s only when they get really light that it becomes a lot of work.