In the World State, the society depicted in the book, there are five castes: Alpha, Beta, Gamma, Delta, and Epsilon. Each caste is conditioned from birth to fulfill specific roles and functions within society.
The Delta caste is the third-lowest caste in the hierarchy. Deltas are physically stronger than the upper castes but are considered less intelligent and have limited intellectual abilities. They are conditioned to perform manual labor and menial tasks. Deltas are generally content with their positions and find fulfillment in their work.
Deltas are also distinguished by their blue uniforms, which signify their caste designation. They are often depicted as being cheerful, hardworking, and dedicated to their roles in the society.
Overall, the caste system in Brave New World, including the Delta caste, serves to maintain social stability and control. Individuals are assigned their positions based on predetermined criteria and are conditioned to accept and embrace their roles, ensuring a smooth functioning of society.