Decisive Riebeckite
Decisive Riebeckite (#577DE3) is a true azure with a vibrant character. It holds its own as a focal accent, carrying visual weight without tipping into neon territory. Its HSL profile (224°, 71%, 62%) 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 amber. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
From the Latin decidere, to cut off — used as a modifier for colors that read as firm and final. Decisive black, decisive red: the implication is that the color has settled on its position and won't drift. Sits in the bold-bucket corner alongside resolute, with a slightly sharper edge.
A sodium-iron amphibole — the source of crocidolite (blue asbestos) and the chatoyant inclusions in hawk's-eye quartz. Mined principally in South Africa and Australia. The color refers to a freshly cleaved riebeckite specimen: a deep, slightly cool dark blue-gray with the slight metallic shine of amphibole.
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.