Thunderous Cobalt
Thunderous Cobalt (#033F86) 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 (213°, 96%, 27%) places it in the highly saturated band at a dark lightness. Best used in small doses, like logos, CTAs, focus rings, or highlight text, where its saturation becomes a feature rather than noise. For a confident two-color system, pair it with its complementary orange. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English thunor, thunder — adjectival suffix -ous, sharing root with German Donner and Old Norse Þórr (Thor). As a color modifier, thunderous implies a deep-and-rumbling-and-imposing-cool quality, the dark cool-gray of cumulonimbus-tower-base storm-cloud directly overhead. Sits at the deep-and-turbulent end of the grid, parallel to stormy with auditory-resonance overtone.
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.