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blue · cool

#40668b

a dark, soft blue · cool · closest name: Royal Blue

Token name suggestion: Slate Denim

RGB
64, 102, 139
HSL
210°, 37%, 40%
CMYK
54, 27, 0, 46
Luminance
0.1246

#40668b is a dark soft blue, 210° on the wheel and 100/100 on the cool side. Put white text on it (6.01:1). As text it scores 6.01:1 on white — safe at any size. Nearest name is Royal Blue, nearest Tailwind family is slate.

hsl(210 37% 40%)rgb(64 102 139)Base step 700AA inkCool

At a glance

Every number on this page in one read: what #40668b is made of, how bright it looks, and which way it leans.

Hex
#40668b
Hue
210°
blue
Saturation
37%
soft
Lightness
40%
dark
Brightness
55%
HSV value
Perceived
38%
weighted brightness
Luminance
0.1246
WCAG relative
Temperature
Cool
100/100 cool
Color family
Blue
Tone
Soft
Best ink
White
6.01:1
Closest name
Royal Blue
ΔE2000 9.7
Chroma
24.6
LCH, 0–130ish
OKLCH L
0.498
perceptual lightness
Tailwind
slate
500 · ΔE 8.5
Web-safe
#336699
nearest of 216
Where it sits
Hue210° of 360°
Saturation37%
Lightness40%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #40668b.

Temperature
Warm ← → Cool100% cool

Reads cool. Warm and cool siblings keep the same lightness, so you can swap one in without redoing your contrast maths.

Luminance by channel
Red9%
Green76%
Blue15%

Green carries most of what the eye calls brightness — that is why WCAG weights it 0.7152.

Every format

HEX#40668b
HEX (8-digit)#40668bff
RGBrgb(64, 102, 139)
RGBArgba(64, 102, 139, 1)
HSLhsl(210, 37%, 40%)
HSV / HSBhsv(210, 54%, 55%)
HWBhwb(210 25% 45%)
CMYKcmyk(54%, 27%, 0%, 46%)
LABlab(41.9 -2.2 -24.5)
LCHlch(41.9 24.6 264.8)
OKLCHoklch(0.498 0.074 248.9)
XYZ (D65)xyz(11.52, 12.46, 26.22)
Decimal4220555
Display P3color(display-p3 0.251 0.400 0.545)
Web-safe#336699

Copy-ready code

every platformclick to select
/* CSS */
color: #40668b;
background-color: #40668b;
/* CSS custom property */
--brand: #40668b;
/* Tailwind (arbitrary) */
class="text-[#40668b] bg-[#40668b]"
/* SCSS */
$brand: #40668b;
/* SwiftUI */
Color(red: 0.251, green: 0.400, blue: 0.545)
/* UIKit */
UIColor(red: 0.251, green: 0.400, blue: 0.545, alpha: 1)
/* Android XML */
<color name="brand">#40668B</color>
/* Android Compose */
Color(0xFF40668B)
/* Flutter */
Color(0xFF40668B)
/* Python / OpenCV (BGR) */
(139, 102, 64)
/* Python / PIL (RGB) */
(64, 102, 139)
/* Java AWT */
new Color(64, 102, 139)
/* .NET */
Color.FromArgb(255, 64, 102, 139)
/* OpenGL / Unity (0–1) */
(0.2510f, 0.4000f, 0.5451f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{64,102,139}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #40668b 85%, white);
border-color: color-mix(in oklab, #40668b 40%, transparent);
/* theme-aware in one line */
color: light-dark(#284057, #D5E1EC);
/* relative colour syntax */
--hover: hsl(from #40668b h s calc(l - 7));

Design tokens

The same ramp in the four formats a team actually needs. Paste one and the whole palette lands with it.

css custom propertiesclick to select
:root {
  --brand-50: #F5F7FA;
  --brand-100: #EBF0F4;
  --brand-200: #D3DEE9;
  --brand-300: #B2C7DC;
  --brand-400: #8CABCA;
  --brand-500: #658FB8;
  --brand-600: #4D7BA8;
  --brand-700: #40668b;
  --brand-800: #335270;
  --brand-900: #283D52;
  --brand-950: #192633;
  --brand: #40668b;
  --brand-ink: #ffffff;
  --brand-surface: #F5F7FA;
  --brand-border: #C7D6E5;
  --brand-hover: #355473;
  --brand-pressed: #2A425A;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #141C24;
    --brand-ink: #D5E1EC;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F5F7FA',
        100: '#EBF0F4',
        200: '#D3DEE9',
        300: '#B2C7DC',
        400: '#8CABCA',
        500: '#658FB8',
        600: '#4D7BA8',
        700: '#40668b',
        800: '#335270',
        900: '#283D52',
        950: '#192633',
        DEFAULT: '#40668b',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F5F7FA,
  '100': #EBF0F4,
  '200': #D3DEE9,
  '300': #B2C7DC,
  '400': #8CABCA,
  '500': #658FB8,
  '600': #4D7BA8,
  '700': #40668b,
  '800': #335270,
  '900': #283D52,
  '950': #192633,
);
$brand-base: #40668b;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F5F7FA", "$type": "color" },
      "100": { "$value": "#EBF0F4", "$type": "color" },
      "200": { "$value": "#D3DEE9", "$type": "color" },
      "300": { "$value": "#B2C7DC", "$type": "color" },
      "400": { "$value": "#8CABCA", "$type": "color" },
      "500": { "$value": "#658FB8", "$type": "color" },
      "600": { "$value": "#4D7BA8", "$type": "color" },
      "700": { "$value": "#40668b", "$type": "color" },
      "800": { "$value": "#335270", "$type": "color" },
      "900": { "$value": "#283D52", "$type": "color" },
      "950": { "$value": "#192633", "$type": "color" }
    },
    "brandInk": { "$value": "#ffffff", "$type": "color" }
  }
}

Best text color

Only one of black and white can be right. This is the one, with the number that proves it.

Readable at a glance#ffffff on #40668b · 6.01:1
Use #ffffffAA at every size, AAA for large text only.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 6.01:1 · recommended
AA pass · AA large pass · AAA fail
Aa
Black text · 3.49:1
AA fail · AA large pass · AAA fail
Reading the other direction: #40668b as text scores 6.01:1 on white and 3.49:1 on black.
Best tinted ink on it, if plain black or white feels flat: #EEF2F7 at 5.35:1.

Make it accessible

A contrast checker tells you that you failed. This tells you what to ship instead — same hue, same saturation, lightness moved only as far as WCAG demands.

The quick fox
#40668b · 6.01:1
AA on whitealready passes
#40668b
The quick fox
#385979 · 7.31:1
AAA on white−5% L
#385979
The quick fox
#4B78A3 · 4.51:1
AA on black+7% L
#4B78A3
The quick fox
#7399BE · 7.03:1
AAA on black+20% L
#7399BE

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #40668B is enough for headings on white. Non-text elements such as icons, chart strokes and focus rings also sit at 3:1 under WCAG 2.2 (1.4.11).

Accessibility — WCAG contrast

Aa
#40668b on white: 6.01:1
AA ✓ pass · AA-large · AAA
Aa
#40668b on black: 3.49:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #40668b as text on that neutral, and that neutral as text on #40668b.

NeutralRatioBoth directions
White6.01:1AaAa
Slate 505.75:1AaAa
Slate 1005.49:1AaAa
Slate 2004.88:1AaAa
Slate 3004.05:1AaAa
Slate 4002.35:1AaAa
Slate 5001.26:1AaAa
Slate 6001.26:1AaAa
Slate 7001.72:1AaAa
Slate 8002.43:1AaAa
Slate 9002.97:1AaAa
Black3.49:1AaAa
Colour vision deficiency
true color
protanopia · #57678D
deuteranopia · #4D608A
tritanopia · #166F73

Roughly one man in twelve has some form of colour vision deficiency. If any of the three panels above is hard to tell apart from a neighbouring colour in your palette, add a shape, an icon or a label so the meaning does not rest on hue alone.

Color scale — 50 to 950

A Tailwind-shaped ramp built around this exact hex. #40668b is pinned to step 700; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.

#F5F7FA
#EBF0F4
#D3DEE9
#B2C7DC
#8CABCA
#658FB8
#4D7BA8
#40668b
#335270
#283D52
#192633
Base = 700Lightest = 50 · #F5F7FADarkest = 950 · #192633Text step on white = 700
Perceptual ramp — OKLCH

The same eleven steps expressed in OKLCH, where equal lightness numbers actually look equally spaced. HSL ramps go muddy in the yellows and washed out in the blues; this one does not. Modern browsers render it natively — the hex ramp above is the fallback.

50100200300400500600700800900950
oklch tokensclick to select
:root {
  --brand-50: oklch(0.97 0.018 248.9);
  --brand-100: oklch(0.94 0.029 248.9);
  --brand-200: oklch(0.88 0.044 248.9);
  --brand-300: oklch(0.80 0.057 248.9);
  --brand-400: oklch(0.72 0.068 248.9);
  --brand-500: oklch(0.64 0.074 248.9);
  --brand-600: oklch(0.56 0.074 248.9);
  --brand-700: oklch(0.48 0.069 248.9);
  --brand-800: oklch(0.40 0.062 248.9);
  --brand-900: oklch(0.32 0.052 248.9);
  --brand-950: oklch(0.24 0.041 248.9);
}

Colors that work with #40668b

Not a palette — a role sheet. Each swatch answers one question you will hit while building the component.

Text on it#ffffff
White wins here
Surface#F5F7FA
Tinted page background
Border#C7D6E5
Hairlines and dividers
Muted text#4B739B
Captions on the surface
Accent#8F503C
Second voice, not a rival
Dark variant#284057
Hover, pressed, headers
Light variant#EEF2F7
Selected rows, tints
Dark surface#141C24
Dark-mode background
Hover#355473
One step down in lightness
Pressed#2A425A
Two steps down
Disabled#889EB3
Chroma pulled out
Focus ring#3B70A4
Offset from the fill so it reads
Light mode
Everything in its place

Surface, border, heading and body all derive from this one hue, so the screen stays coherent without a second palette.

Primary actionSecondaryBadge
Dark mode
Same hue, inverted

Lightness flips, hue holds. The accent stays the anchor in both themes.

Primary actionSecondaryAccent

In real components

The same eight roles, wired into the interface patterns you will actually build with them. Every state below is a computed value, not a mock-up.

Buttons and states
Save changesHoverPressedDisabled
OutlineSubtleLinkFocused
Form field
you@company.com

Focus ring uses the light variant so the field still reads as one shape.

Send me product updates
Notice
Your export is ready

The file stays available for seven days. Download it before it expires.

NewBetaDraft
Data
Storage used68%
Acme LtdActive
NorthwindTrial
GlobexActive

How to use #40668b

Derived from its contrast, chroma and lightness — not from taste.

Works well for
  • Body text and links on white
  • Charts, tags and secondary surfaces
  • Headers, footers and dark-mode surfaces
  • Brand accents, badges and data highlights
Use with care
  • Black text placed on it
  • Pairing with a same-lightness hue — edges vibrate
Minimum size as text on white
Any size
Safe as a fill behind white type
Yes
Safe as a 1px border on white
Yes

Meaning and mood

What a colour in this family tends to signal, and how this particular chroma and lightness change the reading.

trustedcalmcompetentcorporate

The default of institutions for a reason: blue is read as stable and safe across nearly every culture that has been surveyed.

The muted chroma softens the association — it reads considered rather than loud, which suits long-form and data-heavy screens. The low lightness adds weight and formality.

Worth knowing

It is also the most crowded hue on the web. Distinctiveness has to come from your other choices.

Reads as
  • FormalityHigh
  • EnergyMedium
  • Weight60/100
  • TemperatureCool
  • ApproachabilityReserved

Colour associations are cultural and vary by market. Treat these as a starting point for a conversation with your audience, not a finding about them.

Similar colors

One move away from this hex in each direction. Every swatch is its own page.

Color relationships

The wheel positions with their names attached, so you can grab the one you actually need.

Complementary#8B6540
Analogous left#408B8A
Analogous right#40418B
Split-complement 1#8B4041
Split-complement 2#8B8A40
Triadic 1#8B4066
Triadic 2#668B40
Tetradic#8A408B
On the wheel
Base+30°−30°+120°+240°+180°210°

#40668b sits at 210°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red25.1%
Green40.0%
Blue54.5%
R · 0–255
64
0x40
G · 0–255
102
0x66
B · 0–255
139
0x8b

CMYK percentages

Cyan54.0%
Magenta26.6%
Yellow0.0%
Key (black)45.5%

Total ink coverage is 126%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#40668b text on a black background

contrast 3.49:1

Card sample

#40668b text on a white background

contrast 6.01:1

Card sample

#40668b on grey

5.49:1

#40668b on its own surface

5.60:1

#40668b on its dark surface

2.86:1

CSS3 live lab

Text font color

The quick brown fox

color: #40668b;
Background color
Panel with #40668b background
background-color: #40668b;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #40668b;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(64, 102, 139, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(64, 102, 139, 0.45);
Border & gradient
Gradient panel
border: 3px solid #40668b;
background: linear-gradient(135deg, #40668b, #4C408B);
Gradient text

Gradient headline

background: linear-gradient(90deg, #40668b, #5F408B);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #40668b;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #40668b;
caret-color: #40668b;
Left rule
Pull quote or callout
border-left: 4px solid #40668b;
Ring + tint
Selected chip
background: #EEF2F7;
box-shadow: inset 0 0 0 2px #40668b;
Conic badge
68%
background: conic-gradient(#40668b 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #40668b over white; the bottom row is the same alpha over a checkerboard, so you can see what survives on a photo or a video.

Bottom row of hexes is the flattened result over white — use those when a design tool refuses transparency, or when you need a solid fallback.

alpha in every syntaxclick to select
rgba(64, 102, 139, 0.5)
rgb(64 102 139 / 50%)
#40668b80
hsl(210 37% 40% / 50%)
color-mix(in srgb, #40668b 50%, transparent)
Alpha8-digit hexFlat on white
10%#40668b1a#ECF0F3
20%#40668b33#D9E0E8
40%#40668b66#B3C2D1
60%#40668b99#8CA3B9
80%#40668bcc#6685A2

Gradients from #40668b

Six recipes, each built from this hex and shown with the exact CSS that produced it.

Elevation
Same hue, three lightnesses — safe anywhere
background: linear-gradient(135deg, #5785B1, #40668b 45%, #284057);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #40668b, #463676);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #40668b, #8B6540);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #6C94BB 0%, #40668b 45%, #284057 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F5F7FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #50AEA5 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #504AA0 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #284057 0%, transparent 65%), #40668b;

Monochromatic scale

Palettes built from #40668b

Shades — darker

Tints — lighter

Tones — desaturated

Color harmonies

Nearest named colors

Ranked with CIEDE2000 across all 139 CSS keywords. Under ΔE 2 the eye stops telling them apart; over ΔE 10 they are plainly different colors.

#40668b in the real world

Where a color in this family tends to land, and the interface roles it is usually asked to play.

Industries
TechnologyFinanceHealthcareEnterprise SaaS
Common UI roles
ButtonsLinksFocus statesCharts
Print note

Converts to four-color process without much drama. Proof it anyway.

On screens

Holds up across typical panel gamma. Still worth checking on an uncalibrated laptop, where mid-tones shift most.

In dark mode

Too dim on dark surfaces at 3.49:1 — lift it to #4B78A3 for body text, or reserve it for fills.

Explore nearby colors

Small, deliberate steps away from this hex — useful when you are hunting for the version of a colour that finally feels right.

#40668b, answered

What color is #40668b?

#40668b is a dark soft blue, closest to Royal Blue (ΔE2000 9.7). It sits at 210° on the hue wheel with 37% saturation and 40% lightness, which reads as cool.

What is the RGB value of #40668b?

rgb(64, 102, 139) — 64 red, 102 green and 139 blue out of 255, or 25.1% / 40% / 54.5% by channel.

What is #40668b in HSL and HSV?

hsl(210, 37%, 40%) and hsv(210, 54%, 55%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #40668b a light or a dark color?

It is a dark color. Relative luminance is 0.1246 and perceived brightness is 38%, so white text on it reaches 6.01:1.

Should I use black or white text on #40668b?

White. It scores 6.01:1 against #40668b, versus 3.49:1 for black — AA at any size.

Is #40668b accessible on a white background?

#40668b on white scores 6.01:1, which clears AA at every size but not AAA.

What is the complementary color of #40668b?

#8B6540 sits directly opposite on the wheel. Softer options are the split-complements #8B4041 and #8B8A40, which give the same contrast with far less vibration.

What colors go well with #40668b?

For interface work: #F5F7FA as the surface, #C7D6E5 for borders, #4B739B for secondary text, #8F503C as an accent and #284057 for hover and pressed states. For a palette, the analogous pair #408B8A and #40418B stays calm, while #8B6540 is the loudest partner.

What is #40668b in CMYK for printing?

cmyk(54%, 27%, 0%, 46%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.

Is #40668b warm or cool?

Cool — it scores 100 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #404B8B; nudged cooler, #36577B.

Which Tailwind color is closest to #40668b?

The slate family — its 500 step is #64748b, ΔE2000 8.5 away. That is a visible difference, so define #40668b as a custom token rather than reaching for the built-in.

How do I use #40668b in Tailwind CSS?

Inline it as an arbitrary value with bg-[#40668b] or text-[#40668b], or register the whole ramp under theme.extend.colors.brand so you get bg-brand-500 and friends. The generated 50–950 scale on this page is ready to paste into your config.

What is #40668b with 50% opacity?

rgba(64, 102, 139, 0.5), or #40668b80 in eight-digit hex. Over white that composites to #A0B3C5; over black, #203346.

Is #40668b a web-safe color?

No. The nearest web-safe colour is #336699, ΔE2000 2.6 away. The palette only matters for legacy displays and some email clients now.

What does the color #40668b mean?

As a blue, it reads trusted, calm, competent. The default of institutions for a reason: blue is read as stable and safe across nearly every culture that has been surveyed. At this moderate chroma the association is present but not shouted.

What gradient works with #40668b?

The safest is same-hue elevation: linear-gradient(135deg, #5785B1, #40668b 45%, #284057). For more colour, a short hue run to #463676 keeps it rich without turning muddy.

Work with #40668b in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #40668b at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.