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Sure Ophiuchus Ocean

#518687
Notes

Sure Ophiuchus Ocean (#518687) is a true cyan with an earthy character. It leans grounded and natural, the kind of color that plays well with wood, clay, linen, and warm neutrals. Its HSL profile (181°, 25%, 42%) places it in the muted 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
#518687
RGB
rgb(81, 134, 135)
HSL
hsl(181, 25%, 42%)
HWB
hwb(181 32% 47%)
OKLCH
oklch(58.4% 0.057 197.3)
P3
color(display-p3 0.3656 0.5202 0.5264)
HSV
hsv(181, 40%, 53%)
LAB
lab(52.45% -17.31 -6.10)
LCH
lch(52.45% 18.35 199.41)
CMYK
cmyk(40%, 1%, 0%, 47%)

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.

Ophiuchus
modifier

Greek Ὀφιοῦχος, serpent-bearer. As a color modifier, ophiuchus implies a serpent-bearer-and-thirteenth-sign-and-Asclepius quality, the visual register of Hellenic-Ophiuchus-and-Asclepius-serpent-bearer hand-serpent-bearer-and-thirteenth-sign-and-Asclepius Hellenic-Ophiuchus-and-Asclepius-serpent-bearer-and-Rod-of-Asclepius ophiuchus-and-serpent-bearer-and-thirteenth-sign surfaces under Hellenic-Ophiuchus-and-Asclepius-serpent-bearer-and-Rod-of-Asclepius autumn-and-November-and-December serpent-bearer-light. Sits at the modifier-and-zodiac end of the grid, parallel to scorpio and sagittarius in usage.

Ocean
noun

The body of saltwater that covers seventy percent of Earth's surface — a single connected mass divided by convention into Atlantic, Pacific, Indian, Southern, and Arctic. The color refers to the average reflectance of mid-depth temperate ocean: a saturated, slightly green-shifted deep blue with the optical depth of a body of water that absorbs all light below the photic zone. Deeper than mediterranean, cooler than peacock.

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.

#518687
Original
#7f8187
Protanopia
#767a87
Deuteranopia
#3a8986
Tritanopia
#7b7b7b
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).
AA Largeon White
4.11:1
The quick brown foxSample body text at normal size. The wcag minimum for body contrast is 4.5:1 (AA) or 7:1 (AAA).
AAon Black
5.11:1

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
##518687
Display P3
Display P3
color(display-p3 0.3656 0.5202 0.5264)
Inside sRGBOKLCH chroma 0.057

This color sits well within the sRGB cube. P3 and sRGB share the gray axis and most desaturated tones, so a P3 display renders this identically to an sRGB display.

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