Electric blues get too large and too aggressive for a 55g tank. I wouldn't put them in anything less than a 75g.
I wouldn't keep johaniis and yellow labs together personally. With a large group of labs you might be ok, but their aggression levels are very different.
If you want another tank with along the same lines of aggression, then I'd go with groups of Cynotilapia afra, Johannis, and Greshakei or Pseudotropheus socolofi albinos.
Or if you want something different, then go with Yellow Labs or P. saulosi, Acei, and Rusty Cichlids or some type of Aulonocara.
Tangs would be a good 2nd African tank I think if you were wanting something a tad different. But there are of course, other Mbuna. I'd just make sure you house some that are along the same temperament.