Meaning of indigo blue

in'digo blue'

Pronunciation: [key]
  1. indigo (def. 4).
  2. a dark-blue, water-insoluble, crystalline powder, CHNO, having a bronzelike luster, the essential coloring principle of which is contained along with other substances in the dye indigo and which can be produced synthetically.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.