Obsidian Shu
Obsidian Shu (#6A2115) is a deep red 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 (8°, 67%, 25%) places it in the balanced band at a dark lightness. It works well as a headline, icon, or deep background in an otherwise light layout, pairing cleanly with cream, bone, and warm neutrals. For a confident two-color system, pair it with its complementary cyan. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Volcanic glass — molten rhyolite cooled too quickly to crystallize. Mined since the Stone Age for blade-edges (sharper than surgical steel) and ground into mirrors by the Aztec priesthood for divination. The color refers to a polished obsidian flake from Mount Hekla or Glass Buttes, Oregon: a deep, slightly blue-shifted black with the high-gloss conchoidal fracture of natural glass. Cooler than onyx, glossier than coal.
Vermillion in Japanese — specifically the cinnabar-derived pigment used since the Heian period to paint Shinto torii gates, temple beams, and the lacquer of imperial seals. The color refers to a freshly painted Inari Shrine torii: a saturated, slightly orange red with the high gloss of layered urushi lacquer. Brighter than crimson, deeper than tangerine, with the sacred-architectural weight of a color reserved for thresholds between human and divine.
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.