Cool Vivianite
Cool Vivianite (#5DDEE3) is a true cyan with a vibrant character. It holds its own as a focal accent, carrying visual weight without tipping into neon territory. Its HSL profile (182°, 71%, 63%) places it in the balanced band at a mid lightness. It works across type, buttons, and borders, saturated enough to feel deliberate but balanced enough to not fight the rest of the palette. For a confident two-color system, pair it with its complementary red. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English cōl, of low temperature — used as a color modifier as the complement to warm. Cool gray, cool blue: the optical impression of a slight blue-green shift, even within otherwise warm or neutral hues. Sits across the crisp, hushed, pale, and neutral buckets.
A hydrated iron phosphate mineral — colorless when freshly exposed, oxidizing to deep blue-green within hours of air exposure. Mined principally in Cornwall and California. The color refers to a fully-oxidized vivianite specimen: a saturated, slightly cool deep blue-green with the slight metallic luster of phosphate mineral.
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.