Sure Keel Verdigris
Sure Keel Verdigris (#5EBCBA) 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 (179°, 41%, 55%) 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.
Etymology
Old French seur, certain — used as a color modifier since the medieval period for hues that read as confident and stable. Sure red, sure blue: moderate saturation combined with optical commitment. Sits at the crisp-bucket center alongside steady and true.
Old Norse kjölr, keel. As a color modifier, keel implies a longitudinal-bottom-spine-of-ship quality, the visual register of Tall-Ship-and-Royal-Navy-Keel hand-laid longitudinal-bottom-spine timber-and-iron-keel tall-ship-and-frigate maritime-architecture surfaces under hull-and-keel maritime hull-bottom light. Sits at the modifier-and-nautical end of the grid, parallel to hull and spar in usage.
The basic copper carbonate that forms on weathered copper and bronze — the pigment scraped from oxidized metal and used in Renaissance painting before being supplanted by more stable greens. The color refers to a thick verdigris on aged copper roofing or the Statue of Liberty's surface: a soft, slightly muted blue-green with the powdery finish of mineral oxide. Cooler than patina, warmer than seafoam, with the archaeological weight of a mineral made by time.
Closest matches
The nearest named color in three reference sources, ranked by perceptual distance (ΔE76 in CIELAB). ΔE < 1 is imperceptible to most viewers; ΔE > 10 is clearly different. When two sources point to the same hex they’re merged into one tile; click any to open that color’s page.
Variations
Click any swatch to exploreHarmonies
Accessibility
How this color appears to viewers with the four major color-vision-deficiency types. Computed via the Machado (2009) physiologically-based model. If a tile matches the original, the color reads the same to that viewer.
The color used as foreground text against pure white and pure black, with the contrast ratio and WCAG 2.1 grade. Aim for AA (4.5:1) for body text and AA Large (3:1) for 18 pt+ headlines; AAA (7:1) is the gold standard for long-form reading surfaces.
Wide gamut
The CSS Color 4 wide-gamut form of this color. Both swatches render the same color on every display — the P3 form only diverges from sRGB when a designer pushes channels outside sRGB's reach.
Moderately saturated colors gain a small bump in P3 — the difference is usually visible side-by-side on wide-gamut hardware but won't change the character of the color.