Synesthesia is a neurologically-based condition in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. The most common form, colored letters and numbers, occurs when someone always sees a certain color in response to a certain letter of the alphabet or number.
"Indigo" has nothing to do with the color of an aura! It is the result of scientific observations by a woman who has the brain disorder called synesthesia.
The term "indigo children" originates with parapsychologist and self-described synesthete and psychic, Nancy Ann Tappe who developed the concept in the 1970's.
Indigo kids: Does the science fly?
Little Boy Blue
True-believer syndrome is a term coined by M. Lamar Keene in his 1976 book The Psychic Mafia. Keene used the term to refer to people who continued to believe in a paranormal event or phenomenon even after it had been proven to have been staged.
Cognitive dissonance was first investigated by Leon Festinger and associates, arising out of a participant observation study of a cult which believed that the earth was going to be destroyed by a flood, and what happened to its members — particularly the really committed ones who had given up their homes and jobs to work for the cult — when the flood did not happen. While fringe members were more inclined to recognize that they had made fools of themselves and to "put it down to experience", committed members were more likely to re-interpret the evidence to show that they were right all along (the earth was not destroyed because of the faithfulness of the cult members).