Color reference

#637B94 color reference

Muted Mid-light Blue

This is a muted, mid-light blue under the deterministic OKLCH hue, lightness, and chroma ranges. Its closest standardized CSS named color is Slate Gray (#708090), measured with straight-line OKLab distance.

Descriptive label
Muted Mid-light Blue
Recommended text
Black · 4.79:1
Relative luminance
0.189567
Build a palette from #637B94 in Palette Generator Convert #637B94 in Color Converter
Formats UI preview Contrast 50–900 scale Harmonies Matches Related colors Color vision Exports

Copyable values

#637B94 in common color formats

Values are calculated from the same opaque sRGB color. Display rounding does not alter the internal calculations.

Color conversions for #637B94
Format Value Action
HEX #637B94
RGB rgb(99 123 148)
HSL hsl(211 19.84% 48.43%)
HSV hsv(211 33.11% 58.04%)
HWB hwb(211 38.82% 41.96%)
XYZ D65 color(xyz-d65 0.175729 0.189563 0.30751)
LAB lab(50.4177% -4.2476 -16.5948)
LCH lch(50.4177% 17.1297 255.6429)
OKLAB oklab(57.3353% -0.016584 -0.044869)
OKLCH oklch(57.3353% 0.047836 249.7159)

Real-world test

Try #637B94 on interface components

Preview the source as a primary action, subtle status, form treatment, and card surface. Persistent state controls help touch and keyboard users inspect the same normal, hover, and active colors.

Normal state uses #637B94 with black text at 4.79:1.

Action

Primary button

Use the controls above or point to and press the button to inspect its visual states.

Status

Subtle alert badge

A 12% source tint over white provides the background; readable text is selected separately.

Ready for review

Form

Border and focus ring

Source ring on white: 4.38:1 · meets the 3:1 non-text threshold where applicable.

Surface

Card component

The selected state becomes the card surface with its strongest black-or-white text pairing.

Design system Color decision ready Review states and surrounding surfaces before shipping.

Accessibility diagnostics

WCAG contrast for exact color pairs

Each result applies only to the named foreground, background, text size, and requirement. It is not a complete accessibility or component-conformance claim.

Source #637B94 Exact pair assessment Results for source text on white appear below.

On white

4.38:1

  • Fail AA normal text · 4.5:1
  • Fail AAA normal text · 7:1
  • Pass AA large text · 3:1
  • Pass UI/non-text where applicable · 3:1
Source #637B94 Exact pair assessment Results for source text on black appear below.

On black

4.79:1

  • Pass AA normal text · 4.5:1
  • Fail AAA normal text · 7:1
  • Pass AA large text · 3:1
  • Pass UI/non-text where applicable · 3:1

Use guidance

What this color may be suitable for

Not recommended

Normal-sized text

#637B94 does not reach 4.5:1 on white or Hue Codex paper, so it should not be used there for normal-sized text.

Potential fit

Controls and interface graphics

Against Hue Codex paper, the color reaches 4.19:1. That meets the 3:1 color-contrast threshold where WCAG 1.4.11 applies, but states, shape, and non-color cues still need review.

Readable pairing available

Colored surface or button fill

Black text provides the stronger black/white pairing on #637B94 at 4.79:1. This validates only that text pair, not hover, focus, disabled, or adjacent-color states.

Restrained neutral

Palette role

Its OKLCH chroma of 0.0478 is restrained, which is generally more suitable for surfaces, borders, or neutral system roles than for a vivid accent.

Pair available

Color used as foreground

The stronger black/white background is black at 4.79:1. Always retest against the actual rendered background and text size.

Tested backgrounds

Foreground pairing comparison

#637B94 foreground contrast on tested backgrounds
Pair Background Contrast ratio
Black#000000 4.79:1
White#FFFFFF 4.38:1
Hue Codex paper#FBFAF5 4.19:1
Soft neutral#F2EFE6 3.81:1
Hue Codex ink#10212B 3.76:1
Check #637B94 on another background in Contrast Checker

Design-system starting point

A perceptual 50–900 reference scale

The source color is preserved at the nearest lightness step. Other swatches keep its OKLCH hue, moderate chroma toward the extremes, and reduce chroma only when needed to remain in sRGB.

50
100
200
300
400
500 #637B94 Source
600
700
800
900

This is a Hue Codex reference scale, not a claim that the values match Tailwind, Material, or another framework’s named palette.

Adjust the #637B94 scale in Tints, Shades & Tones

Color relationships

Complementary, analogous, and triadic colors

Hue rotations use OKLCH while preserving lightness and requested chroma. When a rotated result falls outside sRGB, chroma is reduced deterministically and disclosed.

Complementary

Source #637B94
Complement

Analogous

Source #637B94
Analogous −30°
Analogous +30°

Triadic

Source #637B94
Triad +120°
Triad +240°

Applied pairing

A small interface check

The source anchors the main action while the complement marks a secondary status. Contrast is selected separately for each fill.

Project color Muted Mid-light Blue
Complement
Explore #637B94 in Color Harmonies

Distance matching

Closest standardized and framework colors

Matches use straight-line OKLab distance ×100. A smaller value means the coordinates are closer in this model; it is not a claim that two tokens are interchangeable in a design system.

CSS named color

Slate Gray

#708090

OKLab distance ×100: 2.56

Tailwind v4 default

slate-500

oklch(55.4% 0.046 257.417)

OKLab distance ×100: 2.04 · sRGB preview #62748E

Print boundary

Pantone match not estimated

Reliable print matching needs licensed reference data plus a defined ink, paper, profile, and viewing condition.

Read the print methodology

Color-vision screening

Approximate color-vision-deficiency views

These encoded-sRGB matrix previews are screening approximations. They help reveal possible color-only distinctions but do not reproduce every person’s vision or establish accessibility conformance.

Original#637B94
Approx.

Protanopia

Red-vision deficiency approximation

Original#637B94
Approx.

Deuteranopia

Green-vision deficiency approximation

Original#637B94
Approx.

Tritanopia

Blue-yellow deficiency approximation

Original#637B94
Approx.#777777

Achromatopsia

Monochromatic-vision approximation

Test #637B94 with a complete palette in the CVD Simulator

Ready to use

Copy framework-ready color tokens

Exports preserve the source, readable foreground, and generated 50–900 scale. Tailwind v4 CSS-first and Tailwind v3 JavaScript-config formats are labeled separately.

CSS custom properties

Semantic aliases and the complete 50–900 scale.

:root {
  --color-primary: #637B94;
  --color-on-primary: #000000;
  --color-primary-oklch: oklch(57.3353% 0.047836 249.7159);
  --color-primary-50: #EEF6FF;
  --color-primary-100: #CFE0F3;
  --color-primary-200: #B3C7DB;
  --color-primary-300: #98ADC3;
  --color-primary-400: #7E95AC;
  --color-primary-500: #637B94;
  --color-primary-600: #4F667D;
  --color-primary-700: #3B4F64;
  --color-primary-800: #273A4D;
  --color-primary-900: #142536;
}

Tailwind v4 CSS-first theme

Current @theme syntax for bg-brand, text-brand, and scale utilities.

@import "tailwindcss";

@theme {
  --color-brand: #637B94;
  --color-brand-foreground: #000000;
  --color-brand-50: #EEF6FF;
  --color-brand-100: #CFE0F3;
  --color-brand-200: #B3C7DB;
  --color-brand-300: #98ADC3;
  --color-brand-400: #7E95AC;
  --color-brand-500: #637B94;
  --color-brand-600: #4F667D;
  --color-brand-700: #3B4F64;
  --color-brand-800: #273A4D;
  --color-brand-900: #142536;
}

Tailwind v3 / legacy config

CommonJS theme.extend.colors for JavaScript-config projects.

module.exports = {
  theme: {
    extend: {
      colors: {
        brand: {
          '50': '#EEF6FF',
          '100': '#CFE0F3',
          '200': '#B3C7DB',
          '300': '#98ADC3',
          '400': '#7E95AC',
          '500': '#637B94',
          '600': '#4F667D',
          '700': '#3B4F64',
          '800': '#273A4D',
          '900': '#142536',
          DEFAULT: '#637B94',
          foreground: '#000000',
        },
      },
    },
  },
};

Sass variables

Semantic source, foreground, OKLCH, and scale variables.

$color-primary: #637B94;
$color-on-primary: #000000;
$color-primary-oklch: oklch(57.3353% 0.047836 249.7159);
$color-primary-50: #EEF6FF;
$color-primary-100: #CFE0F3;
$color-primary-200: #B3C7DB;
$color-primary-300: #98ADC3;
$color-primary-400: #7E95AC;
$color-primary-500: #637B94;
$color-primary-600: #4F667D;
$color-primary-700: #3B4F64;
$color-primary-800: #273A4D;
$color-primary-900: #142536;

Modern color-mix()

Static fallbacks followed by OKLab tint and shade declarations.

:root {
  --color-primary: #637B94;
  --color-primary-tint: #B3C7DB;
  --color-primary-tint: color-mix(in oklab, var(--color-primary) 72%, white);
  --color-primary-shade: #3B4F64;
  --color-primary-shade: color-mix(in oklab, var(--color-primary) 82%, black);
}

JSON design data

Source formats, readable text, and the generated scale.

{
    "name": "Muted Mid-light Blue",
    "hex": "#637B94",
    "rgb": "rgb(99 123 148)",
    "oklch": "oklch(57.3353% 0.047836 249.7159)",
    "recommendedText": "#000000",
    "scale": {
        "50": "#EEF6FF",
        "100": "#CFE0F3",
        "200": "#B3C7DB",
        "300": "#98ADC3",
        "400": "#7E95AC",
        "500": "#637B94",
        "600": "#4F667D",
        "700": "#3B4F64",
        "800": "#273A4D",
        "900": "#142536"
    }
}

Continue the decision

Use #637B94 in a complete workflow

Reference values are a starting point. Test the color in its real role, background, states, typography, and surrounding palette before shipping.

Adjust #637B94 in Color PickerStart with this exact color and white as the working background for role and accessibility decisions. Build a palette from #637B94 in Palette GeneratorUse this exact HEX as the seed for a deterministic, role-based palette. Check #637B94 on white in Contrast CheckerStart with this color as the foreground and white as the background, then test the real pair.