A character with this name is Indigo Casson (male) from the Casson Family books by Hilary McKay. The book from his point of view is the second one, Indigo's Star.
The Indigo Girls are a band made up of Emily Saliers and Amy Ray. They first started performing in 1984, but it wasn't until 1989, with the release of their self-titled album, that their great songwriting and fantastic harmonies gained national attention. They have been nominated for several Grammy awards and won one for Best Contemporary Folk Recording.Their most recognizable singles include "Closer to Fine," "Kid Fears," and "Least Complicated."