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Functional Hill Lagoon

#21c3db
Notes

Functional Hill Lagoon (#21C3DB) 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 (188°, 74%, 49%) 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.

HEX
#21c3db
RGB
rgb(33, 195, 219)
HSL
hsl(188, 74%, 49%)
HWB
hwb(188 13% 14%)
OKLCH
oklch(75.1% 0.125 210.9)
P3
color(display-p3 0.3646 0.7536 0.8460)
HSV
hsv(188, 85%, 86%)
LAB
lab(72.54% -30.48 -23.07)
LCH
lch(72.54% 38.23 217.13)
CMYK
cmyk(85%, 11%, 0%, 14%)

Etymology

Functional
adjective

Latin fūnctiō, performance — adjectival suffix -al. As a color modifier, functional implies a clear-and-purpose-fit-and-utilitarian quality, the crisp color of Mid-Century-Modern and Bauhaus form-follows-function design-aesthetic. Sits at the crisp-and-functional end of the grid, parallel to practical and utilitarian in usage.

Hill
modifier

Old English hyll, natural elevation. As a color modifier, hill implies a rolling-rise-and-pasture quality, the visual register of South-Downs-and-Cotswolds rolling chalk-and-limestone hill-pasture-and-sheep-grazed open surfaces under broad rolling-hill English-pastoral sky. Sits at the modifier-and-place end of the grid, parallel to dale and bluff in usage.

Lagoon
noun

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 explore

Harmonies

Accessibility

Color-vision simulation

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.

#21c3db
Original
#b0bcdc
Protanopia
#98abdb
Deuteranopia
#00cdca
Tritanopia
#a2a2a2
Achromatopsia
WCAG contrast

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.

The quick brown foxSample body text at normal size. The wcag minimum for body contrast is 4.5:1 (AA) or 7:1 (AAA).
Failon White
2.12:1
The quick brown foxSample body text at normal size. The wcag minimum for body contrast is 4.5:1 (AA) or 7:1 (AAA).
AAAon Black
9.89:1

Wide gamut

Display P3 representation

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.

sRGB hex
sRGB hex
##21C3DB
Display P3
Display P3
color(display-p3 0.3646 0.7536 0.8460)
P3 has subtle headroomOKLCH chroma 0.125

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.

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