indigo

noun (plural indigos or indigoes)

• 1a tropical plant of the pea family, which was formerly widely cultivated as a source of dark blue dye.

  • Genus Indigofera, family Leguminosae: several species, in particular I. tinctoria

• 2 [mass noun] the dark blue dye obtained from the indigo plant.
• a colour between blue and violet in the spectrum:the deepest indigo of the horizon