It started out in the 1970's after a book was published on the idea. The author believed that more and more children were being born with an indigo aura and that these children would change our world for the better. Indigo is believed to be a sign of a high spiritual connection when found in the aura, hence the idea these kids were special. The concept of indigo children caught on quickly and during the 80's a lot of people claimed their kids were such. It was actually used as an excuse for ADHD, rebellious behavior and other things considered negative..."She her lack of listening to authority figures is because she is so independent...its from her being an indigo child". I kid you not, this stuff was done. Of course, others say that indigo children actually have unique talents and gifts that make them stand out. They are natural artists, musicians and etc and I'm talking beyond the normal talented folks....you know the kind you see a tv special on or in a facebook posting about how amazing they are.
However, here is my opinion on the matter. Most children have an innocence to them. This is why they are often said to be closer to god (or spirit, deity, etc) than others. Heck, the bible even says one should become like children in order to reach heaven. If you believe in this concept and you don't have to be christian for that, it would make sense they would have an indigo aura...its the color associated with spirit. Those I know who can read aura colors will say that a baby starts out with an indigo/blue colored aura that will adjust over time. I've seen this too with the children I have watched grow up. Therefore, it isn't that the indigo aura thing is new....it just wasn't paid attention to. Maybe those who grow up and still have an indigo aura are special but that is a different deal. However, I've seen auras change over time. Being born with a certain color aura doesn't make anyone more special than anyone else.