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Phosphoric Sour Turquoise

#18f5ff
Notes

Phosphoric Sour Turquoise (#18F5FF) is a true cyan with a neon character. It sits at the high-saturation edge of its family. Use it sparingly, as signage, accent, or highlight against darker surfaces. Its HSL profile (183°, 100%, 55%) places it in the highly saturated band at a mid lightness. Best used in small doses, like logos, CTAs, focus rings, or highlight text, where its saturation becomes a feature rather than noise. 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
#18f5ff
RGB
rgb(24, 245, 255)
HSL
hsl(183, 100%, 55%)
HWB
hwb(183 9% 0%)
OKLCH
oklch(88.3% 0.148 200.2)
P3
color(display-p3 0.4487 0.9467 0.9897)
HSV
hsv(183, 91%, 100%)
LAB
lab(88.31% -43.13 -18.33)
LCH
lch(88.31% 46.86 203.03)
CMYK
cmyk(91%, 4%, 0%, 0%)

Etymology

Phosphoric
adjective

Greek phōsphóros, light-bringer — adjectival suffix -ic. As a color modifier, phosphoric implies a saturated-and-cool-glow quality, the bright color of match-tip-strike and firefly phosphorus-emission luminescence. Sits at the bright-and-cool end of the grid, parallel to phosphorescent and fluorescent in usage.

Sour
modifier

Old English sūr, acid-or-fermented. As a color modifier, sour implies a fermented-and-puckered-and-acid quality, the visual register of sourdough-and-Bavarian-sauerkraut-sour hand-fermented-and-puckered-and-acid sourdough-and-Bavarian-sauerkraut-sour-and-Belgian-Lambic sour-and-fermented-and-puckered surfaces under sourdough-and-Bavarian-sauerkraut-sour-and-Belgian-Lambic San-Francisco-sourdough-and-Brussels-Lambic fermented-puckered-light. Sits at the modifier-and-flavor end of the grid, parallel to tart and tang in usage.

Turquoise
noun

The hydrated copper-aluminum phosphate mined in Persia and the American Southwest for thousands of years — the firuze of Iran, the chalchihuitl of Mesoamerica, the heart of Pueblo and Navajo silverwork. The color refers to a fine Sleeping Beauty turquoise from Arizona: a saturated, slightly green-shifted blue with the slight matrix of host-rock veining. Brighter than persian, lighter than cerulean.

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.

#18f5ff
Original
#e2e9ff
Protanopia
#c5d5ff
Deuteranopia
#00fff8
Tritanopia
#c7c7c7
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
1.35:1
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
15.54:1

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
##18F5FF
Display P3
Display P3
color(display-p3 0.4487 0.9467 0.9897)
P3 has subtle headroomOKLCH chroma 0.148

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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