Every chocolate I know is naughtier than every black lab.
We were at an agility seminar this weekend talking to the trainer and discussing behavioral differences in red (heavy red line) dogs and black line dogs, in reference to Aussies and dobes.
Is it a fine science? No, but sometimes it seems to fit very well.
Probably having far more to do with the "breeding for colors" than anything but it makes sense in a strange way, chocolates have been bred for color more than the alternatives, if I remember correctly.