In this case I'd be tempted to go for a tanginykan setup, with maybe a couple of species from the following; leleupi, brichardi, calvus, julidochromis, or cyprichromis
The cyprichromis and leleupi would be the only colorful fish there, though, which is I had the impression was being wanted. Cyprichromis to my understanding are fragile to new tanks (and should also be kept in something bigger than what's being provided IMO) and leleupi are aggressive to one another, and similar looking fish.
The idea is that i'm wanting a tropical tank as close to a marine tank as possible to try and recapture my old reef tank as i'm no longer allowed anything salty (wife's orders) and I think the combination of tank size, setup and my experience with cichlids is suggesting Pseudotropheus saulosi would be the best idea.
One thing I haven't touched one is dither fish. Would they need to be considered? Would something like tetras (cardinals/neons) suffice as they would add colour too?
Most tetras will die in the high ph. There isn't a lot that can go in an mbuna tank aside from more mbuna. Dithers are not necessary (and IMO shouldn't be used) as its not as though these fish are remotely shy. Saulosi IMO is your best bet for this tank, plenty of color and don't get too big.