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Sure Helen Lagoon

#42bdd4
Notes

Sure Helen Lagoon (#42BDD4) is a true cyan with a cool character. It leans cool, sitting on the blue, green, and violet side of the wheel. Quiet and dependable, a fit for product UI and data visualization. Its HSL profile (189°, 63%, 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
#42bdd4
RGB
rgb(66, 189, 212)
HSL
hsl(189, 63%, 55%)
HWB
hwb(189 26% 17%)
OKLCH
oklch(74.0% 0.111 212.6)
P3
color(display-p3 0.4032 0.7313 0.8194)
HSV
hsv(189, 69%, 83%)
LAB
lab(71.08% -26.34 -21.43)
LCH
lch(71.08% 33.96 219.13)
CMYK
cmyk(69%, 11%, 0%, 17%)

Etymology

Sure
adjective

Old French seur, certain — used as a color modifier since the medieval period for hues that read as confident and stable. Sure red, sure blue: moderate saturation combined with optical commitment. Sits at the crisp-bucket center alongside steady and true.

Helen
modifier

Greek Ἑλένη, Helen-of-Troy. As a color modifier, helen implies a Helen-of-Troy-and-fairest-face quality, the visual register of Helen-of-Troy-and-Tyndareus-Sparta hand-Helen-of-Troy-and-fairest-face Helen-of-Troy-and-Tyndareus-Sparta-and-Iliad-Homeric helen-and-Helen-of-Troy-and-fairest-face surfaces under Helen-of-Troy-and-Tyndareus-Sparta-and-Iliad-Homeric Mycenaean-and-Trojan Bronze-Age-Aegean-light. Sits at the modifier-and-myth end of the grid, parallel to eros and hera 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.

#42bdd4
Original
#abb7d5
Protanopia
#97a7d4
Deuteranopia
#00c6c4
Tritanopia
#a5a5a5
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
2.22:1
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
9.46:1

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
##42BDD4
Display P3
Display P3
color(display-p3 0.4032 0.7313 0.8194)
P3 has subtle headroomOKLCH chroma 0.111

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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