Deep Halo
Deep Halo (#38217E) is a deep indigo 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 (255°, 58%, 31%) 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
Old English dēop, profound, far down — sharing root with dive and dipper. In color shorthand, deep implies low lightness combined with high saturation: a deep red is darker than crimson but no less chromatic. Where dark describes value alone, deep implies that the hue still has presence at that low light level. Closer to rich than to somber.
Greek hálōs, threshing floor — adopted into Christian iconography as the circular disc behind the head of saintly figures, traditionally rendered in ultramarine lapis-and-gold-leaf in Greek-school and Russian-school icon panels. Halo color refers to a 14th-century Russian-school Theotokos icon's halo field: a saturated, slightly cool deep blue-violet with the matte finish of egg-tempera-bound ultramarine over gesso ground.
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.