Sure Reservoir
Sure Reservoir (#0378B3) is a true 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 (200°, 97%, 36%) places it in the highly saturated band at a mid 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 French seur, certain — used as a color modifier since the medieval period for hues that read as confident and stable. Sure red, sure blue: moderate saturation combined with optical commitment. Sits at the crisp-bucket center alongside steady and true.
A constructed body of water — particularly the dam-impounded reservoirs of arid-region water supply: Lake Mead, Hetch Hetchy, Lake Powell. Reservoir color refers to mid-depth Lake Mead water: a saturated, slightly cool deep blue with the optical depth of stored desert water.
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.