The male is called a peacock, the female a peahen. The females are 86 cm (centimeters) long and weigh 2.75–4 kg (kilograms). The males are an average length of about 212 cm in full breeding plumage (107 cm when not) and weigh 4–6 kg. The Indian Peacock has iridescent blue-green plumage. The upper tail coverts on its back are elongated and ornate with an eye at the end of each feather. These are the Peacock's display feathers. The female plumage is a mixture of vibrant yellow, dark purple, deep red and iridescent blue, with the greenish-grey predominating. In the breeding season, females stand apart by lacking the long 'tail feathers' also known as train. Interestingly in the non-breeding season they can be distinguished from males by the green color of the neck as opposed to the blue on the males. The colors result from the micro-structure of the feathers and the resulting optical phenomena.

Peafowl are most notable for the male's extravagant display feathers which, despite actually growing from their back, are known as a 'tail' or train. This train in reality is not the tail but the enormously elongated upper tail coverts. The tail itself is brown and short as in the peahen.

The ornate train is believed to be the result of female sexual selection as males raised the feathers into a fan and quiver it as part of courtship display. Research suggests that peahens select males on the basis of their plumage. The plumage also is an indication of the health of the male.