About indigo
The deep blue-purple Newton inserted between blue and violet in the rainbow. The plant dye behind it built entire colonial trade economies.
The values above are computed from the sRGB hex #4B0082. The OKLCH
form (oklch(33.9% 0.1793 301.68)) is worth noting: unlike HSL, its lightness matches
how bright the colour actually looks, which makes building consistent shade scales far
easier. To tweak this colour or convert one of your own, open the full
colour converter, and check readable text pairings
with the contrast figures shown above.
Accessibility note: text needs a contrast ratio of at least 4.5:1 for normal body copy under WCAG AA. Against white this colour scores 12.95:1 and against black 1.62:1 — use whichever clears the bar for the text you place on it.