Certain Neptune Ruby
Certain Neptune Ruby (#C6204D) is a true red with a vibrant character. It holds its own as a focal accent, carrying visual weight without tipping into neon territory. Its HSL profile (344°, 72%, 45%) 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 teal. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin certus, fixed / sure — sharing root with English concern and certify. As a color modifier, certain implies a saturated-and-unambiguous quality where the hue declares its character without hesitation. Sits at the bold-and-confident end of the grid, parallel to assured and decisive in usage.
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.
From the Latin ruber — simply, red. The gemstone is a chromium-tinged corundum, harder than anything in nature except diamond, and so saturated that a fine Burmese pigeon's blood ruby at auction outpaces a comparable diamond by weight. The color borrows the gem's confidence: a clear, glassy red without the brown of garnet or the blue of crimson.
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.