A kind of deep blue, one of the seven prismatic colors.
A blue dyestuff obtained from several plants belonging to very different genera and orders; as, the woad, Isatis tinctoria, Indigofera tinctoria, I. Anil, Nereum tinctorium, etc. It is a dark blue earthy substance, tasteless and odorless, with a copper-violet luster when rubbed. Indigo does not exist in the plants as such, but is obtained by decomposition of the glycoside indican.
Having the color of, pertaining to, or derived from, indigo.