If you'd like to try and get a Chocolate Palomino:
Palomino x Liver Chestnut (or just a very dark chestnut)
Cremello x Liver Chestnut (or dark chestnut)
Cremello x Flaxen Liver Chestnut
-Little note: Flaxen Liver Chestnuts look a lot similar to Chocolate Palominos with the flaxen mane and tail. Except for liver chestnuts lack that really rich chocolate color that makes the Chocolate Palominos what they are. I used to own a liver chestnut, he was dark, but not chocolate ^^
Silver Dapple Dilution (like what Vidaloco's mare carries) x Liver, or dark, Chestnut
There's probably a million other combination's, and a whole novel about the genetics, but you basically want that dark gene with the creme mixed in.
If your trying for a Chocolate, don't go for a black without the silver dilution. Otherwise you'll probably just end up with a black, buckskin, or palomino foal.
My first guess would be black, though, since black is a dominate gene.
Chocolate Palomino's are beautiful. I'm a total sucker for flaxen horses