Caliginous Virtus Cobalt
Caliginous Virtus Cobalt (#173D81) is a deep azure 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 (218°, 70%, 30%) 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 amber. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin cālīginōsus, misty / dark — derived from cālīgō (mist, gloom). As a color modifier, caliginous implies an obscured, dimmed, slightly-cool-shifted quality where the hue is veiled by darkness or atmospheric fog. Sits at the deep-and-veiled end of the grid, between murky and tenebrous in usage.
Latin virtus, manliness-and-courage-and-virtue. As a color modifier, virtus implies a Roman-virtus-and-stoic-and-Cardinal-Virtues quality, the visual register of Roman-virtus-and-Stoic-Cardinal-Virtues hand-Roman-virtus-and-stoic-and-Cardinal-Virtues Roman-virtus-and-Stoic-Cardinal-Virtues-and-Marcus-Aurelius virtus-and-Roman-virtus surfaces under Roman-virtus-and-Stoic-Cardinal-Virtues-and-Marcus-Aurelius Republican-Rome-and-Marcus-Aurelius Stoic-virtue-light. Sits at the modifier-and-Latin end of the grid, parallel to senex and dux in usage.
Element Co, atomic number 27 — German Kobold, goblin, named by miners who found the metal interfered with smelting silver ore. Cobalt blue is the cobalt-aluminate pigment introduced by Louis Jacques Thénard in 1802: a saturated, slightly green-shifted deep blue with the matte finish of mineral pigment in oil. Cooler than ultramarine, warmer than prussian, with the painter's weight of a pigment used by Renoir, Van Gogh, and Cézanne.
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.