Obsidian Eustoma
Obsidian Eustoma (#171C56) is a deep blue 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 (235°, 58%, 21%) 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 yellow. 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.
Mexican-Texan prairie gentian (Eustoma grandiflorum) — marketed worldwide as lisianthus, a long-stemmed cut-flower industry staple with deep-violet rose-form blooms. Eustoma color refers to a freshly cut Eustoma grandiflorum fully opened bloom: a saturated, slightly cool deep blue-violet with the velvet finish of overlapping ruffled tepals. The Greek genus name eu-stoma means fine-mouthed, after the wide-throated corolla.
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.