Its really all according to your preference. 1200+ different species, almost any color, size, shape.
I can suggest what types there are and we can move from there?
Malawi- Most variety in different colors
Mbuna, colorful males and females alike, fairly aggressive, rocky habitat, needs caves and such for hiding and territory, generally stays 7'' and below. Stay away from plants, they tend to dig and destroy and or uproot plants.
Peacocks, one of the most colorful types, but generally only in the males, females are usually a drab tan or grey, and very hard to tell apart, more docile, but yet still territorial, prefer a mix of rocky and open swimming area, size generally up to 6"
Haps, Extremely colorful males, and also most cases females lack the impressive coloring but are easier to distiguish species, prefer mostly open swimming areas, large variety of sizes ranging from 4" to 15"
Victorians- Among the most colorful of all Cichlids, but many however may be difficult to tell apart until full sexual maturity, Females mostly less colorful but can range from gold, silver, and greens. Victorian Haps are getting more and more rare in the wild due to pollution and destruction of habitat. Many are sought after for this rarity and beauty. Sizes generally 7" and below
Tanganyikans- The MOST diverse choices of all 3 of the major lakes, with size, shape, patterns, and colors. Although generally not as colorful as the other two lakes, the unique diversity along with many genus and species makes them great fish to keep. Because of high demand and difficult collection points for some species, they are some of the most expensive of the Rift Lake Cichlids. Sizes range from the small "sardine cichlids" at up to 3" to the more large and popular Frontosas which can reach well over 12"
Pros and Cons-
Mbuna- PROS- More color selections, ability to "overstock", higher availablitity, and lower price. CONS- Most Aggressive, must take particular care in species stocking.
Peacocks- PROS- Beautiful fins and Colors, Lots of color choices. CONS- Availibility Increasing recently but, hard to find in some locations, especially more sought after species, Many hybrids in the LFS due to difficulty in determining species of females. Usually high prices for the colored Males, where as juveniles are cheap because distinguishing males from females while small is nearly impossible.
Haps- PROS- Good mix of the two previously mentioned regarding color and behavior, Prices are not cheap but not very expensive either. CONS- Only limited species readily availible locally.
Victorians- PROS- Very beautiful, very rare. CONS- Very rare, sometimes hard to find certain species. Price usually follows with the rarity
Tanganyikans- PROS- very large selection to choose from, in both color and size. CONS- Typically very expensive, some 1" fry being anywhere from $10 - $25 each
Thanks