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Frank Deneb Lagoon

#21bfdf
Notes

Frank Deneb Lagoon (#21BFDF) 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 (190°, 75%, 50%) 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
#21bfdf
RGB
rgb(33, 191, 223)
HSL
hsl(190, 75%, 50%)
HWB
hwb(190 13% 13%)
OKLCH
oklch(74.3% 0.127 216.3)
HSV
hsv(190, 85%, 87%)
LAB
lab(71.49% -27.23 -26.84)
LCH
lch(71.49% 38.24 224.59)
CMYK
cmyk(85%, 14%, 0%, 13%)

Etymology

Frank
adjective

From the Old French franc, free, sincere — used as a color modifier since the seventeenth century for hues that read as direct and unhedged. Frank red, frank brown: moderate-to-high saturation combined with optical directness. Sits at the crisp-bucket alongside direct and honest.

Deneb
modifier

Arabic dhanab-al-dajājah, tail-of-the-hen. As a color modifier, deneb implies a Cygnus-tail-and-summer-triangle quality, the visual register of Cygnus-Swan-and-Summer-Triangle-Deneb hand-Cygnus-tail-and-summer-triangle Cygnus-Swan-and-Summer-Triangle-and-Bortle-1-sky deneb-and-Cygnus-tail-and-summer-triangle surfaces under Cygnus-Swan-and-Summer-Triangle-and-Bortle-1-sky July-and-August-summer-vista white-supergiant-stellar-light. Sits at the modifier-and-cosmic end of the grid, parallel to vega and altair 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

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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.

#21bfdf
Original
#aab9e1
Protanopia
#92a8df
Deuteranopia
#00cac9
Tritanopia
#a0a0a0
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
2.19:1
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
9.58:1

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