Calm Buttercup
Calm Buttercup (#667009) is a deep yellow with a jewel character. It carries the deep, saturated richness of a gemstone. Authoritative and slightly formal, it works well for type and heavy UI elements. Its HSL profile (66°, 85%, 24%) places it in the highly saturated band at a dark 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 blue. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin calma, heat of the day — paradoxically drifted in Italian to mean stillness. Used as a color modifier since the seventeenth century for hues that read as untroubled. Calm blue, calm gray: moderate saturation combined with optical quiet. Sits at the crisp-bucket near quiet and steady.
Ranunculus acris and its meadow cousins — the small, glossy yellow flowers of European pastures whose petals reflect ultraviolet light to attract bees. The color refers to a buttercup petal in full sun: a saturated, slightly cool yellow with the polished finish of an epidermis that scatters light like wet paint. The folk test for whether you like butter — holding the flower under your chin to catch its yellow reflection — works on every variety.
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.