Crepuscular Steel
Crepuscular Steel (#18216B) is a deep blue 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 (233°, 63%, 26%) 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 amber. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin crepusculāris, of twilight — derived from crepusculum (twilight). As a color modifier, crepuscular implies the deep blue-violet darkness of civil-twilight period between sunset and nightfall. Sits at the deep-and-cool end of the grid, where the hue carries the Belt of Venus atmospheric-scattering quality of clear-sky horizon at dusk.
An iron-carbon alloy hardened by heat treatment — and steel blue refers specifically to the blue oxide layer that forms on tempered steel as it's heated through 290°C, the temper colors a blacksmith reads to gauge the correct hardness. The color is the blue of a freshly tempered file: a soft, slightly muted gray-blue with the metallic finish of an oxidation layer. Cooler than slate, warmer than denim.
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.