What color is dark indigo?

Deep indigo: A kind of blue with purple. Morphological characteristics of indigo: The organic dye Deep Blue is fermented from leaves of plants containing indole acid, such as Polygonum cuspidatum, Isatis indigotica, Indigo edulis, Malaya, etc., and it is also made artificially (ancient books say that all five kinds of blues can be indigo-Song Ying Xing's Heavenly Creations). The color used to dye cloth can last for a long time. Known as indigo, some areas are called indigo.