Bright Buttercup
Bright Buttercup (#99C005) is a true yellow with a warm character. It leans warm, pulling light toward red, orange, and yellow. Naturally inviting, it suits editorial and hospitality contexts. Its HSL profile (73°, 95%, 39%) 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 indigo. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English beorht, shining, luminous — cognate with the German Bracht, splendor. Applied to color since at least the medieval period for hues that read as luminous: not just light in value but optically active, as if scattering more light back than a dimmer color of the same lightness would. Sits at the bright-bucket center alongside vivid and brilliant.
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.
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.
This color is chromatic enough that authoring it as P3 native (instead of clamping to sRGB) gives a perceptibly more saturated render on wide-gamut displays — modern Macs, iPhones, iPads, and most recent OLED laptops.