Verdigris
Verdigris (#43B3AE) is a true cyan with a cool character. It leans cool, sitting on the blue, green, and violet side of the wheel. Quiet and dependable, a fit for product UI and data visualization. Its HSL profile (177°, 46%, 48%) places it in the balanced band at a mid lightness. It works across type, buttons, and borders, saturated enough to feel deliberate but balanced enough to not fight the rest of the palette. For a confident two-color system, pair it with its complementary red. For something softer, pull in its analogous neighbors on either side of the wheel. Copper plates suspended over vinegar produced this green-blue acetate. The only strong green available to medieval illuminators, though notorious for darkening and eating through parchment over time.