The yellow labs are quite possibly the least aggressive from that list, and probably the most popular Mbuna. They'll mate like crazy too if you are into having little ones! I've had luck with keeping yellow labs with red and blue zebras, johanni, kenyi, acei and trewavasse. I think I've got more males than females when it comes to the blue cobalts, so they tend to chase on another, but other than that, it's a fairly peaceful and active Mbuna mix.