Phosphoric Steller
Phosphoric Steller (#6699FC) 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 (220°, 96%, 69%) 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 amber. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Greek phōsphóros, light-bringer — adjectival suffix -ic. As a color modifier, phosphoric implies a saturated-and-cool-glow quality, the bright color of match-tip-strike and firefly phosphorus-emission luminescence. Sits at the bright-and-cool end of the grid, parallel to phosphorescent and fluorescent in usage.
Cyanocitta stelleri, the Steller's jay — named for German naturalist Georg Wilhelm Steller, who collected the type specimen on the 1741 Bering Expedition. The males display saturated deep-blue plumage with black crests. The color refers to a male Steller's jay in fresh plumage: a saturated, slightly cool deep blue with the matte finish of structurally-colored corvid feathers.
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.