To me, some of the most colorful, yet relatively peaceful cichlids of South America, are the Gymnogeophagines.
They are non-piscavorine and inept at predation (slow), stay relatively small (7"), and will tolerate smallish tanks like 55 gal or 75s.
Easily kept with Buenos Aires tetras, Cory's, and other species from Uruguay, Argentina and other parts of southern S America.
And a bonus, easily kept at room temp (no heater needed)