It is, indeed, that deep, and it applies to the flags of the UK, the Netherlands, and France as well. Sources and further reading: Lemire, Beverly. Cotton. Oxford: Berg Publishers, 2011. Feeser, Andrea. Red, White, and Black Make Blue: Indigo in the Fabric of Colonial South Carolina Life. GA: University of Georgia Press, 2013. Greenfield, Amy Butler. A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire. Doubleday, 2005. Miles, Tiya. All That She Carried: The Journey of Ashley’