Source : Webster's Revised Unabridged Dictionary (1913)

Indigo \In"di*go\, n.; pl. {Indigoes}. [F. indigo, Sp. indigo,
   indico, L. indicum indigo, fr. Indicus Indian. See {Indian}.]
   1. A kind of deep blue, one of the seven prismatic colors.

Source : WordNet®

indigo
     n 1: a blue dye obtained from plants or made synthetically [syn:
          {anil}, {indigotin}]
     2: deciduous subshrub of southeastern Asia having pinnate
        leaves and clusters of red or purple flowers; a source of
        indigo dye [syn: {indigo plant}, {Indigofera tinctoria}]
     3: a blue-violet color
     [also: {indigoes} (pl)]

indigoes
     See {indigo}