indigo

Any of various shrubs or herbs of the genus Indigofera in the pea family, having pinnately compound leaves and usually red or purple flowers in axillary racemes.

A dark blue crystalline compound, C16H10N2O2, that is obtained from these plants or produced synthetically and is widely used as a textile dye.

Any of several related plants, especially those of the genera Amorpha and Baptisia.

The hue of that portion of the visible spectrum lying between blue and violet, evoked in the human observer by radiant energy with wavelengths of approximately 420 to 450 nanometers; a dark blue to grayish purple blue.

Same as Japanese indigo.