Smooth Neptune Kingfisher
Smooth Neptune Kingfisher (#299AA7) 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 (186°, 61%, 41%) 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 English smōþ, level, polished — used as a color modifier since the seventeenth century for hues that read as continuous without texture or break. Smooth tan, smooth gray: moderate saturation combined with optical evenness. Sits in the crisp-bucket alongside even.
Latin Neptunus, Roman-god-of-sea-and-eighth-planet. As a color modifier, neptune implies a Roman-god-of-sea-and-deep-blue-eighth-planet quality, the visual register of Roman-Neptune-and-Voyager-2-deep-blue hand-Roman-god-of-sea-and-deep-blue-eighth-planet Roman-Neptune-and-Voyager-2-deep-blue-and-Trevi-Fountain neptune-and-Roman-god-of-sea surfaces under Roman-Neptune-and-Voyager-2-deep-blue-and-Trevi-Fountain Voyager-2-flyby-and-Trevi-Fountain deep-blue-planet-light. Sits at the modifier-and-zodiac end of the grid, parallel to uranus and saturn in usage.
The family Alcedinidae — particularly Alcedo atthis, the European common kingfisher whose iridescent turquoise-blue plumage gives the color its name. The color refers to a male European kingfisher's wing: a saturated, slightly cool deep blue-green with the iridescent satin finish of structurally colored 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.