Smalt
Smalt (#3B6EB0) is a true azure 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 (214°, 50%, 46%) 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 orange. For something softer, pull in its analogous neighbors on either side of the wheel. Powdered cobalt-blue glass, ground finer for darker tones. A cheap substitute for ultramarine in 15th- to 17th-century European painting — its coarse particles give Vermeer's skies their characteristic granular quality.