Simple Onyx
Simple Onyx (#170A21) 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 (274°, 53%, 8%) 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
Latin simplus, single — sharing root with English single and simplex. As a color modifier, simple implies a neutral-and-uncomplicated-and-stripped-down quality where the hue carries the visual register of Shaker-and-Quaker-craft uncomplicated-and-honest hand-built-craft surface-finish. Sits at the neutral-and-stripped-down end of the grid, parallel to unassuming and modest in usage.
A banded variety of chalcedony — alternating layers of black and white silica, mined in Egypt for cosmetic palettes since Predynastic times and carved into Roman cameos that distinguish the head from the field by stone color alone. The color refers to the black layer of a banded onyx: a deep, slightly muted near-black with the matte finish of cryptocrystalline silica. Cooler than coal, warmer than obsidian.
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.