#666581 Color

#666581 is rgb(102, 101, 129) in RGB, hsl(242, 12%, 45%) in HSL, and about cmyk(21%, 22%, 0%, 49%) in CMYK. It has no registered color name of its own — the closest is Rhythm (#777696), clearly related but distinguishable side by side at ΔE 7.18. White text is the more readable choice on this background.

#666581

HEX#666581

RGBrgb(102, 101, 129)

HSLhsl(242, 12%, 45%)

HSVhsv(242, 22%, 51%)

CMYKcmyk(21%, 22%, 0%, 49%)

OKLCHoklch(51.8% 0.044 286.4)

LABlab(43.68% 5.23 -15.52)

LCHlch(43.68% 16.38 288.61)

What #666581 Is Called

Most hex codes have no name: there are 16.7 million of them and a few thousand registered names. These are the named colors nearest to #666581, ordered by CIE76 distance in CIELAB. Anything under about ΔE 2 is a difference most people cannot see.

Rhythm#777696ΔE 7.18 Independence#4C516DΔE 9.12 Old Lavender#796878ΔE 10.3 Black Coral#54626FΔE 10.86 Dark Electric Blue#536878ΔE 10.99 Slate Gray#708090ΔE 13.29

Browse the full index of named colors A-Z or every blue in the library.

#666581 Channel Values

How #666581 breaks down in each color model. Hue is measured in degrees around the color wheel; saturation, lightness, and the CMYK inks are percentages.

Model	Channels	Notes
RGB	R 102 · G 101 · B 129	8-bit channels as sent to the display
HSL	H 242° · S 12% · L 45%	Easiest model for building lighter and darker variants
HSV	H 242° · S 22% · V 51%	Matches the picker in most design tools
CMYK	C 21% · M 22% · Y 0% · K 49%	Approximate ink mix; confirm with an ICC profile before printing
Luminance	5.61:1 vs white · 3.74:1 vs black	WCAG 2.2 relative-luminance contrast ratios

Text Contrast & Accessibility

WCAG 2.2 contrast ratios for text on a #666581 background. AA requires 4.5:1 for normal text and 3:1 for large text; AAA requires 7:1. Contrast is one check, not a full accessibility review.

TextWhite text5.61:1AA normal AA large AAA normal

Fails AABlack text3.74:1AA normal AA large AAA normal

Need a specific ratio against another background? Open #666581 in the contrast checker.

Colors That Go With #666581

Pairings derived from color-wheel relationships. The complementary color sits opposite #666581; analogous colors sit beside it; triadic and split-complementary sets spread evenly around the wheel. Select any swatch for its own breakdown.

Base

Complementary

Analogous

Analogous

Triadic

Triadic

Split comp.

Split comp.

Tints & Shades of #666581

Lighter tints and darker shades built by moving the lightness channel while holding hue and saturation, which is what you want for hover states, backgrounds, and text variants.

Tints

Shades

Want a full 50-950 ramp with semantic roles? Generate design tokens from #666581.

How #666581 Looks with Color Vision Deficiency

Simulated with the Viénot, Brettel & Mollon LMS projection model. Anomalous types are rendered as partial versions of the matching dichromacy, which is an approximation rather than a per-person clinical model.

Typical#666581

Protanopia#656581

Protanomaly#666581

Deuteranopia#656581

Deuteranomaly#666581

Tritanopia#626969

Tritanomaly#636773

Achromatopsia#686868

Test a full palette in the color blindness simulator.

Using #666581 in Code

Copy-ready declarations for the places this color usually ends up.

CSS custom property--color-666581: #666581;

CSS backgroundbackground-color: #666581;

Tailwind configcolors: { 'color-666581': '#666581' }

SwiftUIColor(red: 0.400, green: 0.396, blue: 0.506)

Android XML<color name="color_666581">#666581</color>

SVG fillfill="#666581"

More Blue Colors

#666581 sits in the blue family. These are its neighbours across that family's full range, each with its own breakdown.

000024 fafaff 00002e f9fafb 000033 f8fafc 000038 f8f8ff 000042 f5faff 000047 f5f5ff 002147 007dfa 0f52ba 1c39bb 2a3439 372aac 4e3cc3 64609a 7abdff 979aaa b8dbff d6d6ff

#666581 Frequently Asked Questions

What color is #666581?

#666581 is a mid-tone blue — rgb(102, 101, 129) in RGB and hsl(242, 12%, 45%) in HSL. It carries no registered color name of its own; the closest named color is Rhythm (#777696), which is clearly related but distinguishable side by side at a CIE76 distance of 7.18.

What is the RGB value of #666581?

#666581 is rgb(102, 101, 129) — red 102, green 101, and blue 129 on the 0-255 scale.

What is the CMYK value of #666581?

#666581 converts to approximately cmyk(21%, 22%, 0%, 49%). CMYK output is a mathematical approximation for planning; confirm production print colors with your printer and ICC profile.

Should text on #666581 be black or white?

White text is the more readable choice. #666581 scores 5.61:1 against white and 3.74:1 against black, and WCAG 2.2 asks for at least 4.5:1 for normal body text.

Can I write #666581 as a CSS color keyword?

No. #666581 is not one of the CSS color keywords, so it has to be written as a hex, rgb() or hsl() value. The closest keyword is slategray (#708090) at a CIE76 distance of 13.29, which is visibly different.

Open #666581 in a Tool

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Keep exploring: every blue in the color library, the guide to shades of blue, or the full color library.