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cyan · cool

#51cefd

a light, electric cyan · cool · closest name: Sky Blue

Token name suggestion: Linen Reef

RGB
81, 206, 253
HSL
196°, 98%, 66%
CMYK
68, 19, 0, 1
Luminance
0.5298

#51cefd is a light electric cyan, 196° on the wheel and 94/100 on the cool side. Put black text on it (11.60:1). As text it scores 1.81:1 on white — use #027FAE instead. Nearest name is Sky Blue, nearest Tailwind family is cyan.

hsl(196 98% 66%)rgb(81 206 253)Base step 400AAA inkCool

At a glance

Every number on this page in one read: what #51cefd is made of, how bright it looks, and which way it leans.

Hex
#51cefd
Hue
196°
cyan
Saturation
98%
electric
Lightness
66%
light
Brightness
99%
HSV value
Perceived
72%
weighted brightness
Luminance
0.5298
WCAG relative
Temperature
Cool
94/100 cool
Color family
Cyan
Tone
Electric
Best ink
Black
11.60:1
Closest name
Sky Blue
ΔE2000 5.3
Chroma
38.8
LCH, 0–130ish
OKLCH L
0.801
perceptual lightness
Tailwind
cyan
500 · ΔE 9
Web-safe
#66CCFF
nearest of 216
Where it sits
Hue196° of 360°
Saturation98%
Lightness66%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #51cefd.

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
Red3%
Green83%
Blue13%

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

Every format

HEX#51cefd
HEX (8-digit)#51cefdff
RGBrgb(81, 206, 253)
RGBArgba(81, 206, 253, 1)
HSLhsl(196, 98%, 66%)
HSV / HSBhsv(196, 68%, 99%)
HWBhwb(196 32% 1%)
CMYKcmyk(68%, 19%, 0%, 1%)
LABlab(77.9 -20.2 -33.1)
LCHlch(77.9 38.8 238.6)
OKLCHoklch(0.801 0.127 226.8)
XYZ (D65)xyz(43.19, 52.98, 100.86)
Decimal5361405
Display P3color(display-p3 0.318 0.808 0.992)
Web-safe#66CCFF

Copy-ready code

every platformclick to select
/* CSS */
color: #51cefd;
background-color: #51cefd;
/* CSS custom property */
--brand: #51cefd;
/* Tailwind (arbitrary) */
class="text-[#51cefd] bg-[#51cefd]"
/* SCSS */
$brand: #51cefd;
/* SwiftUI */
Color(red: 0.318, green: 0.808, blue: 0.992)
/* UIKit */
UIColor(red: 0.318, green: 0.808, blue: 0.992, alpha: 1)
/* Android XML */
<color name="brand">#51CEFD</color>
/* Android Compose */
Color(0xFF51CEFD)
/* Flutter */
Color(0xFF51CEFD)
/* Python / OpenCV (BGR) */
(253, 206, 81)
/* Python / PIL (RGB) */
(81, 206, 253)
/* Java AWT */
new Color(81, 206, 253)
/* .NET */
Color.FromArgb(255, 81, 206, 253)
/* OpenGL / Unity (0–1) */
(0.3176f, 0.8078f, 0.9922f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{81,206,253}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #51cefd 85%, white);
border-color: color-mix(in oklab, #51cefd 40%, transparent);
/* theme-aware in one line */
color: light-dark(#015C7E, #D3E7EE);
/* relative colour syntax */
--hover: hsl(from #51cefd 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: #F1FAFD;
  --brand-100: #E4F5FC;
  --brand-200: #C1EBFB;
  --brand-300: #90E0FE;
  --brand-400: #51cefd;
  --brand-500: #21C0FC;
  --brand-600: #03B1F2;
  --brand-700: #0293CA;
  --brand-800: #0276A1;
  --brand-900: #065674;
  --brand-950: #043649;
  --brand: #51cefd;
  --brand-ink: #000000;
  --brand-surface: #F4F9FA;
  --brand-border: #C0E0ED;
  --brand-hover: #2EC4FD;
  --brand-pressed: #0ABAFC;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #142024;
    --brand-ink: #D3E7EE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F1FAFD',
        100: '#E4F5FC',
        200: '#C1EBFB',
        300: '#90E0FE',
        400: '#51cefd',
        500: '#21C0FC',
        600: '#03B1F2',
        700: '#0293CA',
        800: '#0276A1',
        900: '#065674',
        950: '#043649',
        DEFAULT: '#51cefd',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F1FAFD,
  '100': #E4F5FC,
  '200': #C1EBFB,
  '300': #90E0FE,
  '400': #51cefd,
  '500': #21C0FC,
  '600': #03B1F2,
  '700': #0293CA,
  '800': #0276A1,
  '900': #065674,
  '950': #043649,
);
$brand-base: #51cefd;
$brand-ink: #000000;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F1FAFD", "$type": "color" },
      "100": { "$value": "#E4F5FC", "$type": "color" },
      "200": { "$value": "#C1EBFB", "$type": "color" },
      "300": { "$value": "#90E0FE", "$type": "color" },
      "400": { "$value": "#51cefd", "$type": "color" },
      "500": { "$value": "#21C0FC", "$type": "color" },
      "600": { "$value": "#03B1F2", "$type": "color" },
      "700": { "$value": "#0293CA", "$type": "color" },
      "800": { "$value": "#0276A1", "$type": "color" },
      "900": { "$value": "#065674", "$type": "color" },
      "950": { "$value": "#043649", "$type": "color" }
    },
    "brandInk": { "$value": "#000000", "$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#000000 on #51cefd · 11.60:1
Use #000000AAA at every size.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 1.81:1
AA fail · AA large fail · AAA fail
Aa
Black text · 11.60:1 · recommended
AA pass · AA large pass · AAA pass
Reading the other direction: #51cefd as text scores 1.81:1 on white and 11.60:1 on black.
Best tinted ink on it, if plain black or white feels flat: #015C7E at 4.09:1.

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
#027FAE · 4.52:1
AA on white−31% L
#027FAE
The quick fox
#015E81 · 7.19:1
AAA on white−40% L
#015E81
The quick fox
#51cefd · 11.60:1
AA on blackalready passes
#51cefd
The quick fox
#51cefd · 11.60:1
AAA on blackalready passes
#51cefd

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #029CD6 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
#51cefd on white: 1.81:1
AA ✗ fail · AA-large · AAA
Aa
#51cefd on black: 11.60:1
AA ✓ pass · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #51cefd as text on that neutral, and that neutral as text on #51cefd.

NeutralRatioBoth directions
White1.81:1AaAa
Slate 501.73:1AaAa
Slate 1001.65:1AaAa
Slate 2001.47:1AaAa
Slate 3001.22:1AaAa
Slate 4001.42:1AaAa
Slate 5002.63:1AaAa
Slate 6004.18:1AaAa
Slate 7005.72:1AaAa
Slate 8008.08:1AaAa
Slate 9009.86:1AaAa
Black11.60:1AaAa
Colour vision deficiency
true color
protanopia · #B5CAFF
deuteranopia · #9DB9FC
tritanopia · #00DCDD

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. #51cefd is pinned to step 400; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.

#F1FAFD
#E4F5FC
#C1EBFB
#90E0FE
#51cefd
#21C0FC
#03B1F2
#0293CA
#0276A1
#065674
#043649
Base = 400Lightest = 50 · #F1FAFDDarkest = 950 · #043649Text step on white = 800
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 0.032 226.8);
  --brand-100: oklch(0.94 0.051 226.8);
  --brand-200: oklch(0.88 0.076 226.8);
  --brand-300: oklch(0.80 0.099 226.8);
  --brand-400: oklch(0.72 0.117 226.8);
  --brand-500: oklch(0.64 0.127 226.8);
  --brand-600: oklch(0.56 0.127 226.8);
  --brand-700: oklch(0.48 0.120 226.8);
  --brand-800: oklch(0.40 0.107 226.8);
  --brand-900: oklch(0.32 0.089 226.8);
  --brand-950: oklch(0.24 0.070 226.8);
}

Colors that work with #51cefd

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

Text on it#000000
Black wins here
Surface#F4F9FA
Tinted page background
Border#C0E0ED
Hairlines and dividers
Muted text#4B859B
Captions on the surface
Accent#FF534F
Second voice, not a rival
Dark variant#015C7E
Hover, pressed, headers
Light variant#E6F8FF
Selected rows, tints
Dark surface#142024
Dark-mode background
Hover#2EC4FD
One step down in lightness
Pressed#0ABAFC
Two steps down
Disabled#D8E2E6
Chroma pulled out
Focus ring#63D4FF
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 #51cefd

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

Works well for
  • Text and icons on dark surfaces
  • Primary buttons and calls to action
  • Focus rings, active and selected states
  • Card and section backgrounds
  • Brand accents, badges and data highlights
Use with care
  • Text of any size on white — fails WCAG AA
  • Full-page backgrounds — tiring over long sessions
  • White text placed on it
  • Thin strokes and 1px borders — they disappear on light UI
  • Pairing with a same-lightness hue — edges vibrate
Minimum size as text on white
Not as text
Safe as a fill behind white type
No — use #015C7E
Safe as a 1px border on white
No — use #029CD6

Meaning and mood

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

cleantechnicalfreshclinical

Cyan reads as water, air and infrastructure: cool, hygienic, engineered.

At this chroma the association is amplified — it will dominate anything placed beside it, so give it space and use it sparingly. The lightness keeps it airy and approachable.

Worth knowing

At high lightness it disappears into white surfaces and thin strokes vanish entirely.

Reads as
  • FormalityLow
  • EnergyHigh
  • Weight35/100
  • 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#FD8051
Analogous left#51FDD6
Analogous right#5178FD
Split-complement 1#FD5178
Split-complement 2#FDD651
Triadic 1#FD51CE
Triadic 2#CEFD51
Tetradic#D651FD
On the wheel
Base+30°−30°+120°+240°+180°196°

#51cefd sits at 196°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red31.8%
Green80.8%
Blue99.2%
R · 0–255
81
0x51
G · 0–255
206
0xce
B · 0–255
253
0xfd

CMYK percentages

Cyan68.0%
Magenta18.6%
Yellow0.0%
Key (black)0.8%

Total ink coverage is 87%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#51cefd text on a black background

contrast 11.60:1

Card sample

#51cefd text on a white background

contrast 1.81:1

Card sample

#51cefd on grey

1.65:1

#51cefd on its own surface

1.71:1

#51cefd on its dark surface

9.19:1

CSS3 live lab

Text font color

The quick brown fox

color: #51cefd;
Background color
Panel with #51cefd background
background-color: #51cefd;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #51cefd;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(81, 206, 253, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(81, 206, 253, 0.45);
Border & gradient
Gradient panel
border: 3px solid #51cefd;
background: linear-gradient(135deg, #51cefd, #515BFD);
Gradient text

Gradient headline

background: linear-gradient(90deg, #51cefd, #7251FD);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #51cefd;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #51cefd;
caret-color: #51cefd;
Left rule
Pull quote or callout
border-left: 4px solid #51cefd;
Ring + tint
Selected chip
background: #E6F8FF;
box-shadow: inset 0 0 0 2px #51cefd;
Conic badge
68%
background: conic-gradient(#51cefd 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #51cefd 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(81, 206, 253, 0.5)
rgb(81 206 253 / 50%)
#51cefd80
hsl(196 98% 66% / 50%)
color-mix(in srgb, #51cefd 50%, transparent)
Alpha8-digit hexFlat on white
10%#51cefd1a#EEFAFF
20%#51cefd33#DCF5FF
40%#51cefd66#B9EBFE
60%#51cefd99#97E2FE
80%#51cefdcc#74D8FD

Gradients from #51cefd

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, #8EDFFE, #51cefd 45%, #015C7E);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #51cefd, #3833FD);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #51cefd, #FD8051);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #ACE8FE 0%, #51cefd 45%, #015C7E 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F4F9FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #83FED8 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #6F84FD 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #015C7E 0%, transparent 65%), #51cefd;

Monochromatic scale

Palettes built from #51cefd

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.

#51cefd in the real world

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

Industries
TechnologyTravelHealthcareMedia
Common UI roles
SurfacesBadgesHighlightsEmpty states
Print note

Sits outside most CMYK gamuts — expect a duller press result, or specify a spot ink.

On screens

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

In dark mode

Usable as-is on a dark surface at 11.60:1.

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.

#51cefd, answered

What color is #51cefd?

#51cefd is a light electric cyan, closest to Sky Blue (ΔE2000 5.3). It sits at 196° on the hue wheel with 98% saturation and 66% lightness, which reads as cool.

What is the RGB value of #51cefd?

rgb(81, 206, 253) — 81 red, 206 green and 253 blue out of 255, or 31.8% / 80.8% / 99.2% by channel.

What is #51cefd in HSL and HSV?

hsl(196, 98%, 66%) and hsv(196, 68%, 99%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #51cefd a light or a dark color?

It is a light color. Relative luminance is 0.5298 and perceived brightness is 72%, so black text on it reaches 11.60:1.

Should I use black or white text on #51cefd?

Black. It scores 11.60:1 against #51cefd, versus 1.81:1 for white — AAA at any size.

Is #51cefd accessible on a white background?

#51cefd on white scores 1.81:1, which fails WCAG AA at every size. Darken it to #027FAE to reach 4.5:1, or #015E81 for 7:1.

What is the complementary color of #51cefd?

#FD8051 sits directly opposite on the wheel. Softer options are the split-complements #FD5178 and #FDD651, which give the same contrast with far less vibration.

What colors go well with #51cefd?

For interface work: #F4F9FA as the surface, #C0E0ED for borders, #4B859B for secondary text, #FF534F as an accent and #015C7E for hover and pressed states. For a palette, the analogous pair #51FDD6 and #5178FD stays calm, while #FD8051 is the loudest partner.

What is #51cefd in CMYK for printing?

cmyk(68%, 19%, 0%, 1%). This is a screen-to-ink approximation — a color this saturated sits outside most CMYK gamuts and will print duller than it looks here.

Is #51cefd 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 #51FDED; nudged cooler, #4FB7FF.

Which Tailwind color is closest to #51cefd?

The cyan family — its 500 step is #06b6d4, ΔE2000 9 away. That is a visible difference, so define #51cefd as a custom token rather than reaching for the built-in.

How do I use #51cefd in Tailwind CSS?

Inline it as an arbitrary value with bg-[#51cefd] or text-[#51cefd], 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 #51cefd with 50% opacity?

rgba(81, 206, 253, 0.5), or #51cefd80 in eight-digit hex. Over white that composites to #A8E7FE; over black, #29677F.

Is #51cefd a web-safe color?

No. The nearest web-safe colour is #66CCFF, ΔE2000 2.8 away. The palette only matters for legacy displays and some email clients now.

What does the color #51cefd mean?

As a cyan, it reads clean, technical, fresh. Cyan reads as water, air and infrastructure: cool, hygienic, engineered. At this chroma the effect is amplified — it will dominate whatever sits beside it.

What gradient works with #51cefd?

The safest is same-hue elevation: linear-gradient(135deg, #8EDFFE, #51cefd 45%, #015C7E). For more colour, a short hue run to #3833FD keeps it rich without turning muddy.

Work with #51cefd in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #51cefd at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.