I invite you to take a tour through images of this colorful bird. I have carefully selected images which has captured the key features of the bird. By seeing these photos, and reading tips below, you will learn to recognize this parakeet better. I encourage you to make your own mental notes of features you find unique and striking.

Photo Courtesy of Shantanu Kuveskar ,Dec 2014
Note that the male parakeet has deep red on its head, almost maroon. There is a thin black collar which starts from the lower beak and gives it the appearance of  a “French cut beard”. The neck below the thin black line is greenish-blue.
Photo Courtesy of  michaelandhelencox @ Northern India,Dec 2011
Note that the female has no “plum head” and no shoulder patchPhoto Courtesy of  michaelandhelencox @ Ranthanbore Fort,Rajasthan,Dec 2011
The white tail tips of both male and female birds confirm its identity as the plum-headed parakeet. Its range is also very helpful to separate it from the similar looking blossom-headed parakeet.

I am planning to add more information about this bird near the photos. Meanwhile, you could read more about this beautiful bird @ Wikipedia.