In Aldous Huxley's Brave New World, there are five genetically-dictated castes that inhabit the New World. In the supposed utopia, these predestined humans are named after the letters of the Greek alphabet: Alphas, Betas, Gammas, Deltas, and Epsilons.
The upper castes such as the Alpha Pluses and Alphas are bred for managerial positions. They have been given creative powers, but they have been conditioned to abhor books and nature. The Director of the Hatchery is an Alpha, for example, as are Bernard Marx and Helmholtz.
Not as intelligent as Alphas, Betas also can be minuses and pluses. They have had some decanting (reducing of the oxygen), but are able to hold jobs that require intelligence. Lenina is a Beta. Like other Betas and Alphas, Lenina is taught to hate Gammas, Epsilons, and Deltas. She makes the comment that she is glad that she is a Beta
because they're so frightfully clever. I'm really awfully glad I'm a Beta, because I don't work so hard. And then we are much better than the Gammas and Deltas. Gammas are stupid. They all wear green, and Delta children wear khaki. Oh no, I don't want to play with Delta children. And Epsilons are still worse. They're too stupid to be able..."
GAMMAS - this caste is dressed in green
DELTAS - this caste is dressed in khaki and other castes are conditioned to hate khaki.
EPSILONS - this group has very little intelligence.
The Gammas, the Deltas, and the Epsilons have the menial jobs. There are many of them bred to do these jobs such as running elevators and cleaning floors.
All the groups are conditioned through electric shock and hypnopoedia, sleep conditioning. Sexual entertainment is also encouraged in the new world.