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blue · cool

#3365cf

a balanced, vivid blue · cool · closest name: Royal Blue

Token name suggestion: Atlas Cobalt

RGB
51, 101, 207
HSL
221°, 62%, 51%
CMYK
75, 51, 0, 19
Luminance
0.1452

#3365cf is a balanced vivid blue, 221° on the wheel and 94/100 on the cool side. Put white text on it (5.38:1). As text it scores 5.38:1 on white — safe at any size. Nearest name is Royal Blue, nearest Tailwind family is indigo.

hsl(221 62% 51%)rgb(51 101 207)Base step 600AA inkCool

At a glance

Every number on this page in one read: what #3365cf is made of, how bright it looks, and which way it leans.

Hex
#3365cf
Hue
221°
blue
Saturation
62%
vivid
Lightness
51%
balanced
Brightness
81%
HSV value
Perceived
42%
weighted brightness
Luminance
0.1452
WCAG relative
Temperature
Cool
94/100 cool
Color family
Blue
Tone
Vivid
Best ink
White
5.38:1
Closest name
Royal Blue
ΔE2000 3.4
Chroma
63.1
LCH, 0–130ish
OKLCH L
0.533
perceptual lightness
Tailwind
indigo
500 · ΔE 8.8
Web-safe
#3366CC
nearest of 216
Where it sits
Hue221° of 360°
Saturation62%
Lightness51%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #3365cf.

Temperature
Warm ← → Cool94% 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
Red5%
Green64%
Blue31%

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

Every format

HEX#3365cf
HEX (8-digit)#3365cfff
RGBrgb(51, 101, 207)
RGBArgba(51, 101, 207, 1)
HSLhsl(221, 62%, 51%)
HSV / HSBhsv(221, 75%, 81%)
HWBhwb(221 20% 19%)
CMYKcmyk(75%, 51%, 0%, 19%)
LABlab(45.0 20.5 -59.7)
LCHlch(45.0 63.1 288.9)
OKLCHoklch(0.533 0.173 262.9)
XYZ (D65)xyz(17.28, 14.51, 60.91)
Decimal3368399
Display P3color(display-p3 0.200 0.396 0.812)
Web-safe#3366CC

Copy-ready code

every platformclick to select
/* CSS */
color: #3365cf;
background-color: #3365cf;
/* CSS custom property */
--brand: #3365cf;
/* Tailwind (arbitrary) */
class="text-[#3365cf] bg-[#3365cf]"
/* SCSS */
$brand: #3365cf;
/* SwiftUI */
Color(red: 0.200, green: 0.396, blue: 0.812)
/* UIKit */
UIColor(red: 0.200, green: 0.396, blue: 0.812, alpha: 1)
/* Android XML */
<color name="brand">#3365CF</color>
/* Android Compose */
Color(0xFF3365CF)
/* Flutter */
Color(0xFF3365CF)
/* Python / OpenCV (BGR) */
(207, 101, 51)
/* Python / PIL (RGB) */
(51, 101, 207)
/* Java AWT */
new Color(51, 101, 207)
/* .NET */
Color.FromArgb(255, 51, 101, 207)
/* OpenGL / Unity (0–1) */
(0.2000f, 0.3961f, 0.8118f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{51,101,207}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #3365cf 85%, white);
border-color: color-mix(in oklab, #3365cf 40%, transparent);
/* theme-aware in one line */
color: light-dark(#183267, #D3DBEE);
/* relative colour syntax */
--hover: hsl(from #3365cf 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: #F4F6FB;
  --brand-100: #E8EDF7;
  --brand-200: #CCD7F0;
  --brand-300: #A4BAEA;
  --brand-400: #7798DF;
  --brand-500: #4976D4;
  --brand-600: #3365cf;
  --brand-700: #274FA5;
  --brand-800: #1F3F84;
  --brand-900: #1A3160;
  --brand-950: #101E3C;
  --brand: #3365cf;
  --brand-ink: #ffffff;
  --brand-surface: #F4F6FA;
  --brand-border: #C0CEED;
  --brand-hover: #2A56B4;
  --brand-pressed: #244997;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #141924;
    --brand-ink: #D3DBEE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F4F6FB',
        100: '#E8EDF7',
        200: '#CCD7F0',
        300: '#A4BAEA',
        400: '#7798DF',
        500: '#4976D4',
        600: '#3365cf',
        700: '#274FA5',
        800: '#1F3F84',
        900: '#1A3160',
        950: '#101E3C',
        DEFAULT: '#3365cf',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F4F6FB,
  '100': #E8EDF7,
  '200': #CCD7F0,
  '300': #A4BAEA,
  '400': #7798DF,
  '500': #4976D4,
  '600': #3365cf,
  '700': #274FA5,
  '800': #1F3F84,
  '900': #1A3160,
  '950': #101E3C,
);
$brand-base: #3365cf;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F4F6FB", "$type": "color" },
      "100": { "$value": "#E8EDF7", "$type": "color" },
      "200": { "$value": "#CCD7F0", "$type": "color" },
      "300": { "$value": "#A4BAEA", "$type": "color" },
      "400": { "$value": "#7798DF", "$type": "color" },
      "500": { "$value": "#4976D4", "$type": "color" },
      "600": { "$value": "#3365cf", "$type": "color" },
      "700": { "$value": "#274FA5", "$type": "color" },
      "800": { "$value": "#1F3F84", "$type": "color" },
      "900": { "$value": "#1A3160", "$type": "color" },
      "950": { "$value": "#101E3C", "$type": "color" }
    },
    "brandInk": { "$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 #3365cf · 5.38:1
Use #ffffffAA at every size, AAA for large text only.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 5.38:1 · recommended
AA pass · AA large pass · AAA fail
Aa
Black text · 3.90:1
AA fail · AA large pass · AAA fail
Reading the other direction: #3365cf as text scores 5.38:1 on white and 3.90:1 on black.
Best tinted ink on it, if plain black or white feels flat: #EAEFFA at 4.67:1.

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
#3365cf · 5.38:1
AA on whitealready passes
#3365cf
The quick fox
#2954B0 · 7.02:1
AAA on white−8% L
#2954B0
The quick fox
#4471D3 · 4.55:1
AA on black+4% L
#4471D3
The quick fox
#7597DF · 7.25:1
AAA on black+16% L
#7597DF

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #3365CF 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
#3365cf on white: 5.38:1
AA ✓ pass · AA-large · AAA
Aa
#3365cf on black: 3.90:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #3365cf as text on that neutral, and that neutral as text on #3365cf.

NeutralRatioBoth directions
White5.38:1AaAa
Slate 505.14:1AaAa
Slate 1004.91:1AaAa
Slate 2004.36:1AaAa
Slate 3003.62:1AaAa
Slate 4002.10:1AaAa
Slate 5001.13:1AaAa
Slate 6001.41:1AaAa
Slate 7001.92:1AaAa
Slate 8002.72:1AaAa
Slate 9003.32:1AaAa
Black3.90:1AaAa
Colour vision deficiency
true color
protanopia · #2072D3
deuteranopia · #0064CD
tritanopia · #007F90

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. #3365cf is pinned to step 600; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.

#F4F6FB
#E8EDF7
#CCD7F0
#A4BAEA
#7798DF
#4976D4
#3365cf
#274FA5
#1F3F84
#1A3160
#101E3C
Base = 600Lightest = 50 · #F4F6FBDarkest = 950 · #101E3CText step on white = 600
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 0.043 262.9);
  --brand-100: oklch(0.94 0.069 262.9);
  --brand-200: oklch(0.88 0.104 262.9);
  --brand-300: oklch(0.80 0.135 262.9);
  --brand-400: oklch(0.72 0.159 262.9);
  --brand-500: oklch(0.64 0.173 262.9);
  --brand-600: oklch(0.56 0.173 262.9);
  --brand-700: oklch(0.48 0.163 262.9);
  --brand-800: oklch(0.40 0.145 262.9);
  --brand-900: oklch(0.32 0.121 262.9);
  --brand-950: oklch(0.24 0.095 262.9);
}

Colors that work with #3365cf

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#F4F6FA
Tinted page background
Border#C0CEED
Hairlines and dividers
Muted text#4B649B
Captions on the surface
Accent#D4752E
Second voice, not a rival
Dark variant#183267
Hover, pressed, headers
Light variant#EAEFFA
Selected rows, tints
Dark surface#141924
Dark-mode background
Hover#2A56B4
One step down in lightness
Pressed#244997
Two steps down
Disabled#AAB4C9
Chroma pulled out
Focus ring#386DDE
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 #3365cf

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
  • Brand accents, badges and data highlights
  • Chart series and data categories
Use with care
  • Full-page backgrounds — tiring over long sessions
  • 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 mid lightness keeps it versatile in both themes.

Worth knowing

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

Reads as
  • FormalityMedium
  • EnergyMedium-high
  • Weight49/100
  • 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#CF9D33
Analogous left#33B3CF
Analogous right#4F33CF
Split-complement 1#CF4F33
Split-complement 2#B3CF33
Triadic 1#CF3365
Triadic 2#65CF33
Tetradic#CF33B3
On the wheel
Base+30°−30°+120°+240°+180°221°

#3365cf sits at 221°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red20.0%
Green39.6%
Blue81.2%
R · 0–255
51
0x33
G · 0–255
101
0x65
B · 0–255
207
0xcf

CMYK percentages

Cyan75.4%
Magenta51.2%
Yellow0.0%
Key (black)18.8%

Total ink coverage is 145%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#3365cf text on a black background

contrast 3.90:1

Card sample

#3365cf text on a white background

contrast 5.38:1

Card sample

#3365cf on grey

4.91:1

#3365cf on its own surface

4.97:1

#3365cf on its dark surface

3.27:1

CSS3 live lab

Text font color

The quick brown fox

color: #3365cf;
Background color
Panel with #3365cf background
background-color: #3365cf;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #3365cf;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(51, 101, 207, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(51, 101, 207, 0.45);
Border & gradient
Gradient panel
border: 3px solid #3365cf;
background: linear-gradient(135deg, #3365cf, #6933CF);
Gradient text

Gradient headline

background: linear-gradient(90deg, #3365cf, #9033CF);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #3365cf;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #3365cf;
caret-color: #3365cf;
Left rule
Pull quote or callout
border-left: 4px solid #3365cf;
Ring + tint
Selected chip
background: #EAEFFA;
box-shadow: inset 0 0 0 2px #3365cf;
Conic badge
68%
background: conic-gradient(#3365cf 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #3365cf 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(51, 101, 207, 0.5)
rgb(51 101 207 / 50%)
#3365cf80
hsl(221 62% 51% / 50%)
color-mix(in srgb, #3365cf 50%, transparent)
Alpha8-digit hexFlat on white
10%#3365cf1a#EBF0FA
20%#3365cf33#D6E0F5
40%#3365cf66#ADC1EC
60%#3365cf99#85A3E2
80%#3365cfcc#5C84D9

Gradients from #3365cf

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, #658ADB, #3365cf 45%, #183267);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #3365cf, #682BB8);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #3365cf, #CF9D33);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #7D9DE0 0%, #3365cf 45%, #183267 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F4F6FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #5CCDD9 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #704CD5 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #183267 0%, transparent 65%), #3365cf;

Monochromatic scale

Palettes built from #3365cf

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.

#3365cf 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 3.90:1 — lift it to #4471D3 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.

#3365cf, answered

What color is #3365cf?

#3365cf is a balanced vivid blue, closest to Royal Blue (ΔE2000 3.4). It sits at 221° on the hue wheel with 62% saturation and 51% lightness, which reads as cool.

What is the RGB value of #3365cf?

rgb(51, 101, 207) — 51 red, 101 green and 207 blue out of 255, or 20% / 39.6% / 81.2% by channel.

What is #3365cf in HSL and HSV?

hsl(221, 62%, 51%) and hsv(221, 75%, 81%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #3365cf a light or a dark color?

It is a dark color. Relative luminance is 0.1452 and perceived brightness is 42%, so white text on it reaches 5.38:1.

Should I use black or white text on #3365cf?

White. It scores 5.38:1 against #3365cf, versus 3.90:1 for black — AA at any size.

Is #3365cf accessible on a white background?

#3365cf on white scores 5.38:1, which clears AA at every size but not AAA.

What is the complementary color of #3365cf?

#CF9D33 sits directly opposite on the wheel. Softer options are the split-complements #CF4F33 and #B3CF33, which give the same contrast with far less vibration.

What colors go well with #3365cf?

For interface work: #F4F6FA as the surface, #C0CEED for borders, #4B649B for secondary text, #D4752E as an accent and #183267 for hover and pressed states. For a palette, the analogous pair #33B3CF and #4F33CF stays calm, while #CF9D33 is the loudest partner.

What is #3365cf in CMYK for printing?

cmyk(75%, 51%, 0%, 19%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.

Is #3365cf warm or cool?

Cool — it scores 94 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #3A33CF; nudged cooler, #2A66BF.

Which Tailwind color is closest to #3365cf?

The indigo family — its 500 step is #6366f1, ΔE2000 8.8 away. That is a visible difference, so define #3365cf as a custom token rather than reaching for the built-in.

How do I use #3365cf in Tailwind CSS?

Inline it as an arbitrary value with bg-[#3365cf] or text-[#3365cf], 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 #3365cf with 50% opacity?

rgba(51, 101, 207, 0.5), or #3365cf80 in eight-digit hex. Over white that composites to #99B2E7; over black, #1A3368.

Is #3365cf a web-safe color?

No. The nearest web-safe colour is #3366CC, ΔE2000 0.6 away. The palette only matters for legacy displays and some email clients now.

What does the color #3365cf 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 #3365cf?

The safest is same-hue elevation: linear-gradient(135deg, #658ADB, #3365cf 45%, #183267). For more colour, a short hue run to #682BB8 keeps it rich without turning muddy.

Work with #3365cf in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #3365cf at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.