I'm a fan of short names that are easy for the dog to hear quickly in case you need to call them out of a dangerous situation. I have border collies. They traditionally have short names that can be yelled from a distance. Pete, for instance, is pretty popular for working border collies.
Then we ended up with this husky, which we named Mishka, but call Mo..as in The Mighty Mo. Mo rhymes with no, obviously. It's short but can confuse her if someone tells her "no," which rarely happens. She's not spoiled . We simply don't use "no" very often. We ususally give a comand for the dog to do something other than what it's doing, rather than try to get them to stop doing something that seems perfectly reasonable to them. But that's another story.
So..all that being said, I like Mocha as a name for a chocolate lab. And I'd probably call her Mo.