Look into Chakras alot of the things I learned about auras is from my studies of chakras and subtle energies. If you have any further questions. I will be happy to assist.
From personal experiences:
Most auras are seen to have an egg like shape but not everyone sees aura the same. Many of us will see auras into multiple colors like a painting. Others will just see one aura. Some might see auras in black and white. Others can sense auras through other means such as scent, vibrations and perhaps even more.
The aura is made of subtle energy that is said to be seven layers deep. It holds information about us and help us connect to the psychic plane. The names of the seven layers are calledetheric body, emotional body, mental body, astral layer,ether if template, celestial body and ketheric template. The aura also gives psychic protection.