If you're looking for calm\friendlier cichlids I'd go for Yellow Labs or Rusty (Copper to purple yellow fin accents). Msobo cichlid are kinda like a wild card when it comes to blue\purple colors and they don't get very large.
Rusty cichlids and Msobo only get road round 4" while labs can get up 6".
If you're looking for more color Red and Cobalt blue zebras are pretty chill and they're naturally community fish.
For a 40g I wouldn't put more than 10 fish unless you have really really good filtration. Me personally for a 40g would do 4 Yellow Labs, 2 Msobo and 4 Red Zebra's for lots of contracting colors. Or 2 Labs, 4 Red Zebras, 2 Rusty.
Hope that helps!
The picture is of my fat Msobo and the background fish are M\F Red Top Hongi cichlids
