Buttoned Fast Turquoise
Buttoned Fast Turquoise (#15B4C3) is a true cyan with a vibrant character. It holds its own as a focal accent, carrying visual weight without tipping into neon territory. Its HSL profile (185°, 81%, 42%) places it in the highly saturated band at a mid lightness. Best used in small doses, like logos, CTAs, focus rings, or highlight text, where its saturation becomes a feature rather than noise. 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 bouton, button — past-participle of button. As a color modifier, buttoned implies a clear-and-fastened-and-formal quality, the crisp color of Edwardian-period formal-attire fully-fastened-and-formally-dressed gentleman's-attire. Sits at the crisp-and-finished end of the grid, parallel to trim and pressed in usage.
Old English fæst, abstinence-from-food. As a color modifier, fast implies a Lenten-and-fasting-and-restraint quality, the visual register of Roman-Catholic-and-Eastern-Orthodox-Fast Lenten-and-Ramadan-fasting religious-fast-and-restraint austere surfaces under fasting-and-restraint austere ecclesiastical light. Sits at the modifier-and-time end of the grid, parallel to lent and vigil in usage.
The hydrated copper-aluminum phosphate mined in Persia and the American Southwest for thousands of years — the firuze of Iran, the chalchihuitl of Mesoamerica, the heart of Pueblo and Navajo silverwork. The color refers to a fine Sleeping Beauty turquoise from Arizona: a saturated, slightly green-shifted blue with the slight matrix of host-rock veining. Brighter than persian, lighter than cerulean.
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.