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Cool Mast Lagoon

#40bfdd
Notes

Cool Mast Lagoon (#40BFDD) 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°, 70%, 56%) 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
#40bfdd
RGB
rgb(64, 191, 221)
HSL
hsl(191, 70%, 56%)
HWB
hwb(191 25% 13%)
OKLCH
oklch(74.8% 0.116 217.0)
P3
color(display-p3 0.4026 0.7389 0.8527)
HSV
hsv(191, 71%, 87%)
LAB
lab(71.94% -24.84 -25.03)
LCH
lch(71.94% 35.26 225.22)
CMYK
cmyk(71%, 14%, 0%, 13%)

Etymology

Cool
adjective

Old English cōl, of low temperature — used as a color modifier as the complement to warm. Cool gray, cool blue: the optical impression of a slight blue-green shift, even within otherwise warm or neutral hues. Sits across the crisp, hushed, pale, and neutral buckets.

Mast
modifier

Old English mæst, long-pole. As a color modifier, mast implies a tall-pole-with-sails quality, the visual register of Tall-Ship-and-Royal-Navy-Mast hand-rigged tall-mast-with-sail-and-yard tall-ship-and-frigate maritime-architecture surfaces under tall-ship-mast-and-yard maritime-overhead light. Sits at the modifier-and-nautical end of the grid, parallel to spar and boom 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.

#40bfdd
Original
#abb9df
Protanopia
#95a9dd
Deuteranopia
#00cac8
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
2.16:1
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
9.71:1

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
##40BFDD
Display P3
Display P3
color(display-p3 0.4026 0.7389 0.8527)
P3 has subtle headroomOKLCH chroma 0.116

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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