If you’re looking for peaceful and colorful I’d look into the smaller South American cichlids.
Bolivian rams can be quite colorful when they’ve established themselves in a nice comfy home with good clean water and good food. They reach a good 4″. Comical and spunky they’re very fun to watch.
Apistogramma species stay small and some of them can be quite spectacular. Apisto. borellii, Apisto. nijsseni, A. panduro, A. cacatuoides, A. agassizii, A. baenschi, A. bitaeniata, etc. And most of them get about 3″ long.
Laetacara sp. can color up boldly depending on mood and are a little more cool-hardy than most SA tropicals.
Bujurquina sp. are an interesting South American mouth brooder recently increasing in popularity and availability. Most of them sport a gold base color with tones of blue and/or green on the body or fins and orange around the face/mouth.
Nannacara anomala, and old classic, not as easily found today as it may have been decades ago but a very pretty gold cichlid with spunk!
Even dwarf pikes would do nicely if you could find them. Most stay under 6″ with the smallest reaching 3″ at most. Crenicichla regani and C. compressiceps would be the two most common and they make the round on Aquabid and occasionally pop up in shops. A specialist may be able to get them for you. As with most pikes, they’re highly aggressive toward one another and obtaining a pair can be trying but once established a pair can fend their own in a tank with more boisterous tankmates.
Ever consider the smaller Africans? Non-rift lake of course. Kribs are fiery little mini-monsters. In this species it is the female that vies for the male’s attention and takes the pick. If and when she has become displeased with the male she may rid herself of him. This may be as simple as moving to opposite ends of the tank or flying into a murderous rampage but this situation isn’t only applicable to a female as there’s only so much a little man-fish can take before he finally decided to fight back lol. They’re a dramatic little cichlid and a hobby staple for good reason. They’re easy to keep, spawn and provide plenty of entertainment and activity. Males reach 4″, females not exceeding 2.5″ and you could probably fit yourself with two pairs in that tank.
Anomalochromis thomasi is another spunky African. A bit of attitude, nice gem-like coloration but not as easy to find as they once were. They come in several forms as well, none too different from the other so I wouldn’t get particular.
Chromidotilapia sp. are mouthbrooders, the females of which are usually the more colorful ones when in good condition. They are the “African Eartheaters” as they, superficially, resemble SA’s Satanoperca.
Steatocranus casuarius may not be colorful but they have personality and attitude to make up for it. Males develop a large nuchal hump with age and they have charming blue eyes.
Pseudocrenilabrus nicholsi and P. multicolor are very similar in behavior to Malawian cichlids, as they are polygamous maternal mouthbrooders and in general it is the male who is colorful while the females are a silver/brown color. You would be able to keep a small colony of these without worry for any of your other fish. They are not quite as aggressive as most polygamous mouthbrooding rift-lake cichlids.
For CA’s, some of the less common convict-cousins, such as Cryptoheros sajica, Crypto. spilurus, C. spilurus cutteri, C. sp. Honduran Red Point and C. septemfasciatus would make in interesting set-up if you ended up with just a single pair.
Archocentrus spinosissimus is much more peaceful than most convict types and has to be seen in person to be truly appreciated. They’re not too easy to find but would make beautiful inhabitants as well. A. centrarchus, probably not as colorful as most of the aforementioned, and a little more thick as adults but they are also quite peaceful even while spawning.
Herotilapia multispinosa, the rainbow cichlid, can be found in several forms. Recently a highly orange form has been popularized and become more desired but the normal ones are quite nice showing a range of bronze, copper, gold, and orange tones throughout the body.
Neetroplus panamensis comes primarily in a red form, as it has been desired over the other forms but they are also a gorgeous cichlid with a variable color and pattern most of which is red/pink/orange based.
And last, but not least, give consideration to the less common members of the Thorichthys clan. Thorichthys aureus is occasionally found in local shops and Thorichthys sp. Mixteco Green or T. sp. Mixteco Blue can be found through people who specialize in CA cichlids.