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blue · cool

#371dbf

a dark, vivid blue · cool · closest name: Medium Blue

Token name suggestion: Slate Cobalt

RGB
55, 29, 191
HSL
250°, 74%, 43%
CMYK
71, 85, 0, 25
Luminance
0.0545

#371dbf is a dark vivid blue, 250° on the wheel and 78/100 on the cool side. Put white text on it (10.05:1). As text it scores 10.05:1 on white — safe at any size. Nearest name is Medium Blue, nearest Tailwind family is indigo.

hsl(250 74% 43%)rgb(55 29 191)Base step 700AAA inkCool

At a glance

Every number on this page in one read: what #371dbf is made of, how bright it looks, and which way it leans.

Hex
#371dbf
Hue
250°
blue
Saturation
74%
vivid
Lightness
43%
dark
Brightness
75%
HSV value
Perceived
29%
weighted brightness
Luminance
0.0545
WCAG relative
Temperature
Cool
78/100 cool
Color family
Blue
Tone
Vivid
Best ink
White
10.05:1
Closest name
Medium Blue
ΔE2000 3.6
Chroma
96.8
LCH, 0–130ish
OKLCH L
0.405
perceptual lightness
Tailwind
indigo
500 · ΔE 20.3
Web-safe
#3333CC
nearest of 216
Where it sits
Hue250° of 360°
Saturation74%
Lightness43%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #371dbf.

Temperature
Warm ← → Cool78% 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
Red15%
Green16%
Blue69%

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

Every format

HEX#371dbf
HEX (8-digit)#371dbfff
RGBrgb(55, 29, 191)
RGBArgba(55, 29, 191, 1)
HSLhsl(250, 74%, 43%)
HSV / HSBhsv(250, 85%, 75%)
HWBhwb(250 11% 25%)
CMYKcmyk(71%, 85%, 0%, 25%)
LABlab(28.0 57.1 -78.2)
LCHlch(28.0 96.8 306.1)
OKLCHoklch(0.405 0.227 276.4)
XYZ (D65)xyz(11.42, 5.45, 49.73)
Decimal3612095
Display P3color(display-p3 0.216 0.114 0.749)
Web-safe#3333CC

Copy-ready code

every platformclick to select
/* CSS */
color: #371dbf;
background-color: #371dbf;
/* CSS custom property */
--brand: #371dbf;
/* Tailwind (arbitrary) */
class="text-[#371dbf] bg-[#371dbf]"
/* SCSS */
$brand: #371dbf;
/* SwiftUI */
Color(red: 0.216, green: 0.114, blue: 0.749)
/* UIKit */
UIColor(red: 0.216, green: 0.114, blue: 0.749, alpha: 1)
/* Android XML */
<color name="brand">#371DBF</color>
/* Android Compose */
Color(0xFF371DBF)
/* Flutter */
Color(0xFF371DBF)
/* Python / OpenCV (BGR) */
(191, 29, 55)
/* Python / PIL (RGB) */
(55, 29, 191)
/* Java AWT */
new Color(55, 29, 191)
/* .NET */
Color.FromArgb(255, 55, 29, 191)
/* OpenGL / Unity (0–1) */
(0.2157f, 0.1137f, 0.7490f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{55,29,191}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #371dbf 85%, white);
border-color: color-mix(in oklab, #371dbf 40%, transparent);
/* theme-aware in one line */
color: light-dark(#20116F, #D7D3EE);
/* relative colour syntax */
--hover: hsl(from #371dbf 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: #F4F3FC;
  --brand-100: #EAE7F8;
  --brand-200: #CFC8F3;
  --brand-300: #AB9EF0;
  --brand-400: #816DE9;
  --brand-500: #573CE1;
  --brand-600: #3D20D4;
  --brand-700: #371dbf;
  --brand-800: #29168E;
  --brand-900: #211467;
  --brand-950: #150C40;
  --brand: #371dbf;
  --brand-ink: #ffffff;
  --brand-surface: #F5F4FA;
  --brand-border: #C7C0ED;
  --brand-hover: #2E18A0;
  --brand-pressed: #251481;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #161424;
    --brand-ink: #D7D3EE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F4F3FC',
        100: '#EAE7F8',
        200: '#CFC8F3',
        300: '#AB9EF0',
        400: '#816DE9',
        500: '#573CE1',
        600: '#3D20D4',
        700: '#371dbf',
        800: '#29168E',
        900: '#211467',
        950: '#150C40',
        DEFAULT: '#371dbf',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F4F3FC,
  '100': #EAE7F8,
  '200': #CFC8F3,
  '300': #AB9EF0,
  '400': #816DE9,
  '500': #573CE1,
  '600': #3D20D4,
  '700': #371dbf,
  '800': #29168E,
  '900': #211467,
  '950': #150C40,
);
$brand-base: #371dbf;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F4F3FC", "$type": "color" },
      "100": { "$value": "#EAE7F8", "$type": "color" },
      "200": { "$value": "#CFC8F3", "$type": "color" },
      "300": { "$value": "#AB9EF0", "$type": "color" },
      "400": { "$value": "#816DE9", "$type": "color" },
      "500": { "$value": "#573CE1", "$type": "color" },
      "600": { "$value": "#3D20D4", "$type": "color" },
      "700": { "$value": "#371dbf", "$type": "color" },
      "800": { "$value": "#29168E", "$type": "color" },
      "900": { "$value": "#211467", "$type": "color" },
      "950": { "$value": "#150C40", "$type": "color" }
    },
    "brandInk": { "$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 #371dbf · 10.05:1
Use #ffffffAAA at every size.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 10.05:1 · recommended
AA pass · AA large pass · AAA pass
Aa
Black text · 2.09:1
AA fail · AA large fail · AAA fail
Reading the other direction: #371dbf as text scores 10.05:1 on white and 2.09:1 on black.
Best tinted ink on it, if plain black or white feels flat: #ECE9FC at 8.43:1.

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
#371dbf · 10.05:1
AA on whitealready passes
#371dbf
The quick fox
#371dbf · 10.05:1
AAA on whitealready passes
#371dbf
The quick fox
#7660E7 · 4.60:1
AA on black+21% L
#7660E7
The quick fox
#9888ED · 7.08:1
AAA on black+30% L
#9888ED

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #371DBF 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
#371dbf on white: 10.05:1
AA ✓ pass · AA-large · AAA
Aa
#371dbf on black: 2.09:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #371dbf as text on that neutral, and that neutral as text on #371dbf.

NeutralRatioBoth directions
White10.05:1AaAa
Slate 509.60:1AaAa
Slate 1009.17:1AaAa
Slate 2008.15:1AaAa
Slate 3006.77:1AaAa
Slate 4003.92:1AaAa
Slate 5002.11:1AaAa
Slate 6001.33:1AaAa
Slate 7001.03:1AaAa
Slate 8001.46:1AaAa
Slate 9001.78:1AaAa
Black2.09:1AaAa
Colour vision deficiency
true color
protanopia · #0049C3
deuteranopia · #003BBC
tritanopia · #005272

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. #371dbf 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.

#F4F3FC
#EAE7F8
#CFC8F3
#AB9EF0
#816DE9
#573CE1
#3D20D4
#371dbf
#29168E
#211467
#150C40
Base = 700Lightest = 50 · #F4F3FCDarkest = 950 · #150C40Text step on white = 500
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 0.057 276.4);
  --brand-100: oklch(0.94 0.091 276.4);
  --brand-200: oklch(0.88 0.136 276.4);
  --brand-300: oklch(0.80 0.177 276.4);
  --brand-400: oklch(0.72 0.209 276.4);
  --brand-500: oklch(0.64 0.227 276.4);
  --brand-600: oklch(0.56 0.227 276.4);
  --brand-700: oklch(0.48 0.214 276.4);
  --brand-800: oklch(0.40 0.191 276.4);
  --brand-900: oklch(0.32 0.159 276.4);
  --brand-950: oklch(0.24 0.125 276.4);
}

Colors that work with #371dbf

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#F5F4FA
Tinted page background
Border#C7C0ED
Hairlines and dividers
Muted text#574B9B
Captions on the surface
Accent#B5A717
Second voice, not a rival
Dark variant#20116F
Hover, pressed, headers
Light variant#ECE9FC
Selected rows, tints
Dark surface#161424
Dark-mode background
Hover#2E18A0
One step down in lightness
Pressed#251481
Two steps down
Disabled#9992BA
Chroma pulled out
Focus ring#3414DD
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 #371dbf

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

Works well for
  • Body text and links on white
  • Primary buttons and calls to action
  • Focus rings, active and selected states
  • Headers, footers and dark-mode surfaces
  • Brand accents, badges and data highlights
Use with care
  • Text on black or near-black surfaces
  • Full-page backgrounds — tiring over long sessions
  • 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.

This is a confident chroma: strong enough to lead a brand, restrained enough to live in an interface all day. 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-high
  • Weight57/100
  • 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#A5BF1D
Analogous left#1D54BF
Analogous right#881DBF
Split-complement 1#BF881D
Split-complement 2#54BF1D
Triadic 1#BF371D
Triadic 2#1DBF37
Tetradic#BF1D54
On the wheel
Base+30°−30°+120°+240°+180°250°

#371dbf sits at 250°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red21.6%
Green11.4%
Blue74.9%
R · 0–255
55
0x37
G · 0–255
29
0x1d
B · 0–255
191
0xbf

CMYK percentages

Cyan71.2%
Magenta84.8%
Yellow0.0%
Key (black)25.1%

Total ink coverage is 181%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#371dbf text on a black background

contrast 2.09:1

Card sample

#371dbf text on a white background

contrast 10.05:1

Card sample

#371dbf on grey

9.17:1

#371dbf on its own surface

9.19:1

#371dbf on its dark surface

1.80:1

CSS3 live lab

Text font color

The quick brown fox

color: #371dbf;
Background color
Panel with #371dbf background
background-color: #371dbf;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #371dbf;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(55, 29, 191, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(55, 29, 191, 0.45);
Border & gradient
Gradient panel
border: 3px solid #371dbf;
background: linear-gradient(135deg, #371dbf, #A31DBF);
Gradient text

Gradient headline

background: linear-gradient(90deg, #371dbf, #BF1DB2);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #371dbf;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #371dbf;
caret-color: #371dbf;
Left rule
Pull quote or callout
border-left: 4px solid #371dbf;
Ring + tint
Selected chip
background: #ECE9FC;
box-shadow: inset 0 0 0 2px #371dbf;
Conic badge
68%
background: conic-gradient(#371dbf 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #371dbf 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(55, 29, 191, 0.5)
rgb(55 29 191 / 50%)
#371dbf80
hsl(250 74% 43% / 50%)
color-mix(in srgb, #371dbf 50%, transparent)
Alpha8-digit hexFlat on white
10%#371dbf1a#EBE8F9
20%#371dbf33#D7D2F2
40%#371dbf66#AFA5E5
60%#371dbf99#8777D9
80%#371dbfcc#5F4ACC

Gradients from #371dbf

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, #5338E1, #371dbf 45%, #20116F);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #371dbf, #9819A4);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #371dbf, #A5BF1D);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #6A53E5 0%, #371dbf 45%, #20116F 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F5F4FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #2F7ADF 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #AA21D9 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #20116F 0%, transparent 65%), #371dbf;

Monochromatic scale

Palettes built from #371dbf

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.

#371dbf 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 2.09:1 — lift it to #7660E7 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.

#371dbf, answered

What color is #371dbf?

#371dbf is a dark vivid blue, closest to Medium Blue (ΔE2000 3.6). It sits at 250° on the hue wheel with 74% saturation and 43% lightness, which reads as cool.

What is the RGB value of #371dbf?

rgb(55, 29, 191) — 55 red, 29 green and 191 blue out of 255, or 21.6% / 11.4% / 74.9% by channel.

What is #371dbf in HSL and HSV?

hsl(250, 74%, 43%) and hsv(250, 85%, 75%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #371dbf a light or a dark color?

It is a dark color. Relative luminance is 0.0545 and perceived brightness is 29%, so white text on it reaches 10.05:1.

Should I use black or white text on #371dbf?

White. It scores 10.05:1 against #371dbf, versus 2.09:1 for black — AAA at any size.

Is #371dbf accessible on a white background?

#371dbf on white scores 10.05:1, which clears AAA at every size.

What is the complementary color of #371dbf?

#A5BF1D sits directly opposite on the wheel. Softer options are the split-complements #BF881D and #54BF1D, which give the same contrast with far less vibration.

What colors go well with #371dbf?

For interface work: #F5F4FA as the surface, #C7C0ED for borders, #574B9B for secondary text, #B5A717 as an accent and #20116F for hover and pressed states. For a palette, the analogous pair #1D54BF and #881DBF stays calm, while #A5BF1D is the loudest partner.

What is #371dbf in CMYK for printing?

cmyk(71%, 85%, 0%, 25%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.

Is #371dbf warm or cool?

Cool — it scores 78 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #721DBF; nudged cooler, #1B3CC1.

Which Tailwind color is closest to #371dbf?

The indigo family — its 500 step is #6366f1, ΔE2000 20.3 away. That is a visible difference, so define #371dbf as a custom token rather than reaching for the built-in.

How do I use #371dbf in Tailwind CSS?

Inline it as an arbitrary value with bg-[#371dbf] or text-[#371dbf], 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 #371dbf with 50% opacity?

rgba(55, 29, 191, 0.5), or #371dbf80 in eight-digit hex. Over white that composites to #9B8EDF; over black, #1C0F60.

Is #371dbf a web-safe color?

No. The nearest web-safe colour is #3333CC, ΔE2000 4.7 away. The palette only matters for legacy displays and some email clients now.

What does the color #371dbf 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 chroma the effect is amplified — it will dominate whatever sits beside it.

What gradient works with #371dbf?

The safest is same-hue elevation: linear-gradient(135deg, #5338E1, #371dbf 45%, #20116F). For more colour, a short hue run to #9819A4 keeps it rich without turning muddy.

Work with #371dbf in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #371dbf at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.