An essay examines indigo as a central dye for wool and cotton, tracing its extraction, historical commerce, and practical use in textile manufacture. It describes indigo's exceptional resistance to air and light, its role as a foundation for blacks, greens, and purples, and contrasts its stability with the brighter but fugitive aniline dyes that have displaced it. The text argues for renewed use of indigo on economic and aesthetic grounds, notes manufacturers' and consumers' conflicting preferences, and cites military regulations and industrial practice to illustrate how indigo yields durable, consistent hues in finished fabrics.