Indigo Children
The classification began as one woman's personal aura-reading system in 1982. A 1999 book attached it specifically to childhood behaviour and to scepticism about ADHD diagnosis, launching a wider genre of 'crystal' and 'rainbow' children that followed the same pattern.
Nancy Ann Tappe's aura classification (1982); Lee Carroll & Jan Tober, The Indigo Children (1999)
A New Age belief that certain children are born with a special aura colour marking them as spiritually advanced.