Untroubled Ergo Lagoon
Untroubled Ergo Lagoon (#21B3CE) 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 (189°, 72%, 47%) 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
Latin turbāre, to disturb — negative-prefix un- plus past-participle of trouble. As a color modifier, untroubled implies a clear-and-calm-and-undisturbed quality where the hue carries no visual agitation. Sits at the crisp-and-calm end of the grid, parallel to serene and placid in usage.
Latin ergo, therefore-or-thus. As a color modifier, ergo implies a Latin-logical-and-cogito-ergo-sum quality, the visual register of Cartesian-cogito-ergo-sum hand-Latin-logical-and-cogito-ergo-sum Cartesian-cogito-ergo-sum-and-Scholastic-syllogism ergo-and-Latin-logical-and-cogito-ergo-sum surfaces under Cartesian-cogito-ergo-sum-and-Scholastic-syllogism Sorbonne-Scholastic-and-Cartesian-meditation logical-deduction-light. Sits at the modifier-and-Latin end of the grid, parallel to ipse and opus in usage.
A shallow body of saltwater partially or fully enclosed by a barrier — coral atoll lagoons in the Pacific, Venice's Laguna Veneta, the Florida Keys' backcountry. The color refers to the average reflectance of a calm tropical lagoon at midday: a saturated, slightly muted blue-green with the optical clarity of shallow water over white sand. Brighter than reef, cooler than aquamarine, with the postcard weight of a Pacific atoll seen from above.
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.