Steely Keystone
Steely Keystone (#5C574A) is a deep amber 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 (43°, 11%, 33%) places it in the muted 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 azure. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
An adjectival form of steel — used as a color modifier since the eighteenth century for hues with the slight blue-gray of tempered or polished steel. Steely gray, steely blue: moderate-to-low saturation combined with the optical impression of metallic surface. Sits in the neutral-and-cool corner alongside cold.
Old English cǣg-stān, key-stone — the iconic cool-mid-gray central-arch-stone of medieval European Gothic-arch-and-vault architecture, particularly the Chartres-Cathedral nave-vault keystone tradition. Keystone color refers to a Chartres-Cathedral nave-vault keystone face in raking candlelight: a balanced cool gray with the matte finish of Bercé-Forest-Berchères-limestone hand-quarried-and-hand-cut medieval-cathedral-vault-stone.
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 sits well within the sRGB cube. P3 and sRGB share the gray axis and most desaturated tones, so a P3 display renders this identically to an sRGB display.