"Peacocks" refer to species of the genus Aulonocara and the mass market hybrids which are not pure Aulonocara and may be more aggressive. All "Peacock" males are potentially very attractive, but there is no guarantee of perfect color. Males get colorful when getting mature. Intensity of color depends on pecking order and dominance.
People try to have male only tanks, and hope the males get along and hope that the males show at least some color. One male may become hyperdominant and be a bully. This is not as easy as a community fish tank, it is not as simple as just adding pretty fish together. You need to have it somewhat crowded, like more than 10 cichlids, to even out the social and anti-social interaction. You can have a small Pleco type. Personally, I think your tank is too small to have much of a male tank, so don't spend much money on good fish.
Or you can have a breeding group like James says, but then you would have only one colorful male, which you may not want.