Plain Bluestone
Plain Bluestone (#19161C) 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 (270°, 12%, 10%) 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 lime. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin planus, flat, level — used as a color modifier since the medieval period for hues that read as undecorated and direct. Plain white, plain blue: moderate saturation, no shift, no surface effect. Sits in the crisp-bucket center, with the implication of restraint rather than absence.
Preseli bluestone — the deep-gray-blue spotted-dolerite boulders sourced from the Preseli Hills of West Wales and transported 240 km to Stonehenge (c. 2900 BCE). Bluestone color refers to a Stonehenge inner-circle bluestone face in midday sun: a dark cool-gray with the matte finish of spotted-dolerite with feldspar-and-pyroxene phenocrysts on a Neolithic-quarried boulder.
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
This color has effectively no chroma (OKLCH C = 0.013) — it’s on the grayscale axis. Hue rotations don’t change a grayscale color, so complementary, analogous, triadic, and split-complementary all reduce to the same value. They aren’t shown because four identical tiles would be misleading.
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.