Fathomless Lunar
Fathomless Lunar (#221B63) is a deep blue with a cool character. It leans cool, sitting on the blue, green, and violet side of the wheel. Quiet and dependable, a fit for product UI and data visualization. Its HSL profile (246°, 57%, 25%) 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.
Latin luna, moon — adopted into English as the adjective for moon-related phenomena. The lunar color tradition refers to the deep blue-violet of Apollo-program lunar-orbit Earthrise photography (1968–1972) showing the deep blue limb of Earth over the gray Moon surface. Lunar color refers to a Hasselblad Earthrise photo's deep-Earth limb: a saturated, slightly cool deep blue-violet with the optical complexity of Earth-atmosphere Rayleigh scattering against the lunar void.
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.