Indigos are plants that yield a blue dye, and are part of the Indigofera genus. These plants are native to tropical and subtropical regions, and have been used for centuries to produce a variety of blue dyes. The most common indigo dye is derived from the leaves of the Indigofera tinctoria plant, which is native to India and other parts of Asia. Other species of indigo plants are also used to produce blue dyes, including Indigofera suffruticosa, which is native to South America.