Thunderous Erythrite
Thunderous Erythrite (#311F4E) is a deep indigo with an earthy character. It leans grounded and natural, the kind of color that plays well with wood, clay, linen, and warm neutrals. Its HSL profile (263°, 43%, 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 lime. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English thunor, thunder — adjectival suffix -ous, sharing root with German Donner and Old Norse Þórr (Thor). As a color modifier, thunderous implies a deep-and-rumbling-and-imposing-cool quality, the dark cool-gray of cumulonimbus-tower-base storm-cloud directly overhead. Sits at the deep-and-turbulent end of the grid, parallel to stormy with auditory-resonance overtone.
Cobalt bloom, a hydrated cobalt arsenate mineral that forms as a secondary alteration product on cobalt-rich ores. The mineral is sometimes called cobalt arsenate hydrate. Erythrite color refers to a freshly fractured Schneeberg erythrite crystal cluster: a saturated, slightly cool deep violet with the matte finish of acicular hydrated cobalt-arsenate crystals. Named for the Greek erythros (red), though the mineral is purple-violet.
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.