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Cool Throb Lagoon

#42b9d9
Notes

Cool Throb Lagoon (#42B9D9) 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 (193°, 67%, 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
#42b9d9
RGB
rgb(66, 185, 217)
HSL
hsl(193, 67%, 55%)
HWB
hwb(193 26% 15%)
OKLCH
oklch(73.3% 0.113 219.4)
P3
color(display-p3 0.3972 0.7158 0.8367)
HSV
hsv(193, 70%, 85%)
LAB
lab(70.08% -22.78 -25.69)
LCH
lch(70.08% 34.34 228.44)
CMYK
cmyk(70%, 15%, 0%, 15%)

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.

Throb
modifier

Middle English throbben, to-beat-strongly. As a color modifier, throb implies a pulsing-and-beating-and-rhythmic quality, the visual register of racing-pulse-and-temple-throb hand-pulsing-and-beating-and-rhythmic racing-pulse-and-temple-throb-and-heartbeat throbbed-and-pulsing-and-beating-and-rhythmic surfaces under racing-pulse-and-temple-throb-and-heartbeat fevered-and-quickened-and-rhythmic candlelit-bedside-light. Sits at the modifier-and-mood end of the grid, parallel to pang and pulse 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.

#42b9d9
Original
#a5b4db
Protanopia
#90a5d9
Deuteranopia
#00c4c3
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
2.29:1
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
9.17:1

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
##42B9D9
Display P3
Display P3
color(display-p3 0.3972 0.7158 0.8367)
P3 has subtle headroomOKLCH chroma 0.113

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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