There's lots of options, price will depend on the fish size. They normally start coloring up around 2.5-3", depending on where they are in the hierarchy, some more docile fish may never fully color up, aulonocara maylandi is one that doesn't normally do well in a mixed tank. You have yellows like aulonocara maleri or flavascent, for red you have eureka and German reds, and for blue you have your red shoulders and cobue. There are hundreds of peacocks. The only problem is once you get a red, blue, and yellow then anything that looks close to the same could and probably will fight.