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Sterile Dux Lagoon

#40bfda
Notes

Sterile Dux Lagoon (#40BFDA) 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 (191°, 68%, 55%) 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
#40bfda
RGB
rgb(64, 191, 218)
HSL
hsl(191, 68%, 55%)
HWB
hwb(191 25% 15%)
OKLCH
oklch(74.7% 0.114 215.0)
P3
color(display-p3 0.4026 0.7389 0.8417)
HSV
hsv(191, 71%, 85%)
LAB
lab(71.83% -25.77 -23.56)
LCH
lch(71.83% 34.92 222.43)
CMYK
cmyk(71%, 12%, 0%, 15%)

Etymology

Sterile
adjective

Latin sterilis, barren / not-fertile — sharing root with Greek steiros (barren). As a color modifier, sterile implies a clear-and-medical-clean-and-stripped quality, the crisp color of operating-theater surgical-environment white-and-stainless-steel surfaces. Sits at the crisp-and-clean end of the grid, parallel to sanitary and hygienic in usage.

Dux
modifier

Latin dux, leader-or-general. As a color modifier, dux implies a Latin-leader-and-Roman-general-and-Doge quality, the visual register of Roman-dux-and-Venetian-Doge hand-Latin-leader-and-Roman-general-and-Doge Roman-dux-and-Venetian-Doge-and-Renaissance-condottiere dux-and-Latin-leader surfaces under Roman-dux-and-Venetian-Doge-and-Renaissance-condottiere Republican-Rome-and-Venetian-Doge's-Palace leader-and-general-light. Sits at the modifier-and-Latin end of the grid, parallel to pater and virtus 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.

#40bfda
Original
#acb9dc
Protanopia
#97a9da
Deuteranopia
#00c9c7
Tritanopia
#a6a6a6
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
2.17:1
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
9.68:1

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
##40BFDA
Display P3
Display P3
color(display-p3 0.4026 0.7389 0.8417)
P3 has subtle headroomOKLCH chroma 0.114

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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