Fathomless Sumi
Fathomless Sumi (#371F83) is a deep indigo 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 (254°, 62%, 32%) 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 yellow. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Fathom (Old English fæthm, six-foot span used to measure water-depth) plus suffix -less. As a color modifier, fathomless implies a depth of saturation-and-darkness that resists the eye's attempt to gauge it. Sits at the deepest end of the deep-bucket grid, beyond ordinary measure of color-depth perception.
Japanese ink stick, made from soot of pine resin or sesame oil mixed with animal-glue binder, used in sumi-e brush painting and shodō calligraphy. Although nominally black, undiluted sumi on rice paper carries a deep blue-violet undertone. Sumi color refers to a heavily-loaded sumi brushstroke: a saturated, slightly cool deep blue-violet with the matte finish of pine-soot ink on absorbent washi.
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.