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cyan · cool

#51f3df

a balanced, electric cyan · cool · closest name: Turquoise

Token name suggestion: Atlas Teal

RGB
81, 243, 223
HSL
173°, 87%, 64%
CMYK
67, 0, 8, 5
Luminance
0.7118

#51f3df is a balanced electric cyan, 173° on the wheel and 84/100 on the cool side. Put black text on it (15.24:1). As text it scores 1.38:1 on white — use #098374 instead. Nearest name is Turquoise, nearest Tailwind family is teal.

hsl(173 87% 64%)rgb(81 243 223)Base step 400AAA inkCool

At a glance

Every number on this page in one read: what #51f3df is made of, how bright it looks, and which way it leans.

Hex
#51f3df
Hue
173°
cyan
Saturation
87%
electric
Lightness
64%
balanced
Brightness
95%
HSV value
Perceived
81%
weighted brightness
Luminance
0.7118
WCAG relative
Temperature
Cool
84/100 cool
Color family
Cyan
Tone
Electric
Best ink
Black
15.24:1
Closest name
Turquoise
ΔE2000 4.3
Chroma
46.2
LCH, 0–130ish
OKLCH L
0.876
perceptual lightness
Tailwind
teal
500 · ΔE 14.4
Web-safe
#66FFCC
nearest of 216
Where it sits
Hue173° of 360°
Saturation87%
Lightness64%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #51f3df.

Temperature
Warm ← → Cool84% 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
Red2%
Green90%
Blue7%

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

Every format

HEX#51f3df
HEX (8-digit)#51f3dfff
RGBrgb(81, 243, 223)
RGBArgba(81, 243, 223, 1)
HSLhsl(173, 87%, 64%)
HSV / HSBhsv(173, 67%, 95%)
HWBhwb(173 32% 5%)
CMYKcmyk(67%, 0%, 8%, 5%)
LABlab(87.6 -46.2 -2.6)
LCHlch(87.6 46.2 183.3)
OKLCHoklch(0.876 0.136 183.3)
XYZ (D65)xyz(48.76, 71.17, 80.97)
Decimal5370847
Display P3color(display-p3 0.318 0.953 0.875)
Web-safe#66FFCC

Copy-ready code

every platformclick to select
/* CSS */
color: #51f3df;
background-color: #51f3df;
/* CSS custom property */
--brand: #51f3df;
/* Tailwind (arbitrary) */
class="text-[#51f3df] bg-[#51f3df]"
/* SCSS */
$brand: #51f3df;
/* SwiftUI */
Color(red: 0.318, green: 0.953, blue: 0.875)
/* UIKit */
UIColor(red: 0.318, green: 0.953, blue: 0.875, alpha: 1)
/* Android XML */
<color name="brand">#51F3DF</color>
/* Android Compose */
Color(0xFF51F3DF)
/* Flutter */
Color(0xFF51F3DF)
/* Python / OpenCV (BGR) */
(223, 243, 81)
/* Python / PIL (RGB) */
(81, 243, 223)
/* Java AWT */
new Color(81, 243, 223)
/* .NET */
Color.FromArgb(255, 81, 243, 223)
/* OpenGL / Unity (0–1) */
(0.3176f, 0.9529f, 0.8745f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{81,243,223}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #51f3df 85%, white);
border-color: color-mix(in oklab, #51f3df 40%, transparent);
/* theme-aware in one line */
color: light-dark(#08776A, #D3EEEB);
/* relative colour syntax */
--hover: hsl(from #51f3df 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: #F2FDFB;
  --brand-100: #E5FAF8;
  --brand-200: #C4F7F1;
  --brand-300: #96F8EC;
  --brand-400: #51f3df;
  --brand-500: #2DF1D8;
  --brand-600: #10E5CB;
  --brand-700: #0DBFA9;
  --brand-800: #0B9987;
  --brand-900: #0C6E62;
  --brand-950: #08453D;
  --brand: #51f3df;
  --brand-ink: #000000;
  --brand-surface: #F4FAFA;
  --brand-border: #C0EDE7;
  --brand-hover: #2FF1D9;
  --brand-pressed: #10ECD1;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #142422;
    --brand-ink: #D3EEEB;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F2FDFB',
        100: '#E5FAF8',
        200: '#C4F7F1',
        300: '#96F8EC',
        400: '#51f3df',
        500: '#2DF1D8',
        600: '#10E5CB',
        700: '#0DBFA9',
        800: '#0B9987',
        900: '#0C6E62',
        950: '#08453D',
        DEFAULT: '#51f3df',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F2FDFB,
  '100': #E5FAF8,
  '200': #C4F7F1,
  '300': #96F8EC,
  '400': #51f3df,
  '500': #2DF1D8,
  '600': #10E5CB,
  '700': #0DBFA9,
  '800': #0B9987,
  '900': #0C6E62,
  '950': #08453D,
);
$brand-base: #51f3df;
$brand-ink: #000000;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F2FDFB", "$type": "color" },
      "100": { "$value": "#E5FAF8", "$type": "color" },
      "200": { "$value": "#C4F7F1", "$type": "color" },
      "300": { "$value": "#96F8EC", "$type": "color" },
      "400": { "$value": "#51f3df", "$type": "color" },
      "500": { "$value": "#2DF1D8", "$type": "color" },
      "600": { "$value": "#10E5CB", "$type": "color" },
      "700": { "$value": "#0DBFA9", "$type": "color" },
      "800": { "$value": "#0B9987", "$type": "color" },
      "900": { "$value": "#0C6E62", "$type": "color" },
      "950": { "$value": "#08453D", "$type": "color" }
    },
    "brandInk": { "$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 #51f3df · 15.24:1
Use #000000AAA at every size.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 1.38:1
AA fail · AA large fail · AAA fail
Aa
Black text · 15.24:1 · recommended
AA pass · AA large pass · AAA pass
Reading the other direction: #51f3df as text scores 1.38:1 on white and 15.24:1 on black.
Best tinted ink on it, if plain black or white feels flat: #08776A at 3.95:1.

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
#098374 · 4.66:1
AA on white−36% L
#098374
The quick fox
#076257 · 7.26:1
AAA on white−43% L
#076257
The quick fox
#51f3df · 15.24:1
AA on blackalready passes
#51f3df
The quick fox
#51f3df · 15.24:1
AAA on blackalready passes
#51f3df

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #0BA592 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
#51f3df on white: 1.38:1
AA ✗ fail · AA-large · AAA
Aa
#51f3df on black: 15.24:1
AA ✓ pass · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #51f3df as text on that neutral, and that neutral as text on #51f3df.

NeutralRatioBoth directions
White1.38:1AaAa
Slate 501.32:1AaAa
Slate 1001.26:1AaAa
Slate 2001.12:1AaAa
Slate 3001.08:1AaAa
Slate 4001.86:1AaAa
Slate 5003.45:1AaAa
Slate 6005.50:1AaAa
Slate 7007.51:1AaAa
Slate 80010.61:1AaAa
Slate 90012.95:1AaAa
Black15.24:1AaAa
Colour vision deficiency
true color
protanopia · #E8E5DE
deuteranopia · #D0D4E1
tritanopia · #00F8ED

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. #51f3df 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.

#F2FDFB
#E5FAF8
#C4F7F1
#96F8EC
#51f3df
#2DF1D8
#10E5CB
#0DBFA9
#0B9987
#0C6E62
#08453D
Base = 400Lightest = 50 · #F2FDFBDarkest = 950 · #08453DText step on white = 900
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 0.034 183.3);
  --brand-100: oklch(0.94 0.054 183.3);
  --brand-200: oklch(0.88 0.081 183.3);
  --brand-300: oklch(0.80 0.106 183.3);
  --brand-400: oklch(0.72 0.125 183.3);
  --brand-500: oklch(0.64 0.136 183.3);
  --brand-600: oklch(0.56 0.136 183.3);
  --brand-700: oklch(0.48 0.127 183.3);
  --brand-800: oklch(0.40 0.114 183.3);
  --brand-900: oklch(0.32 0.095 183.3);
  --brand-950: oklch(0.24 0.075 183.3);
}

Colors that work with #51f3df

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#F4FAFA
Tinted page background
Border#C0EDE7
Hairlines and dividers
Muted text#4B9B91
Captions on the surface
Accent#F74D8C
Second voice, not a rival
Dark variant#08776A
Hover, pressed, headers
Light variant#E7FDFB
Selected rows, tints
Dark surface#142422
Dark-mode background
Hover#2FF1D9
One step down in lightness
Pressed#10ECD1
Two steps down
Disabled#D2E2E0
Chroma pulled out
Focus ring#5CFDE9
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 #51f3df

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
  • Brand accents, badges and data highlights
  • Chart series and data categories
Use with care
  • Text of any size on white — fails WCAG AA
  • Full-page backgrounds — tiring over long sessions
  • 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 #08776A
Safe as a 1px border on white
No — use #0BA592

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 mid lightness keeps it versatile in both themes.

Worth knowing

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

Reads as
  • FormalityLow
  • EnergyHigh
  • Weight37/100
  • 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#F35165
Analogous left#51F38E
Analogous right#51B6F3
Split-complement 1#F351B6
Split-complement 2#F38E51
Triadic 1#DF51F3
Triadic 2#F3DF51
Tetradic#8E51F3
On the wheel
Base+30°−30°+120°+240°+180°173°

#51f3df sits at 173°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red31.8%
Green95.3%
Blue87.5%
R · 0–255
81
0x51
G · 0–255
243
0xf3
B · 0–255
223
0xdf

CMYK percentages

Cyan66.7%
Magenta0.0%
Yellow8.2%
Key (black)4.7%

Total ink coverage is 80%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#51f3df text on a black background

contrast 15.24:1

Card sample

#51f3df text on a white background

contrast 1.38:1

Card sample

#51f3df on grey

1.26:1

#51f3df on its own surface

1.31:1

#51f3df on its dark surface

11.67:1

CSS3 live lab

Text font color

The quick brown fox

color: #51f3df;
Background color
Panel with #51f3df background
background-color: #51f3df;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #51f3df;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(81, 243, 223, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(81, 243, 223, 0.45);
Border & gradient
Gradient panel
border: 3px solid #51f3df;
background: linear-gradient(135deg, #51f3df, #519BF3);
Gradient text

Gradient headline

background: linear-gradient(90deg, #51f3df, #5172F3);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #51f3df;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #51f3df;
caret-color: #51f3df;
Left rule
Pull quote or callout
border-left: 4px solid #51f3df;
Ring + tint
Selected chip
background: #E7FDFB;
box-shadow: inset 0 0 0 2px #51f3df;
Conic badge
68%
background: conic-gradient(#51f3df 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #51f3df 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, 243, 223, 0.5)
rgb(81 243 223 / 50%)
#51f3df80
hsl(173 87% 64% / 50%)
color-mix(in srgb, #51f3df 50%, transparent)
Alpha8-digit hexFlat on white
10%#51f3df1a#EEFEFC
20%#51f3df33#DCFDF9
40%#51f3df66#B9FAF2
60%#51f3df99#97F8EC
80%#51f3dfcc#74F5E5

Gradients from #51f3df

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, #8AF7EA, #51f3df 45%, #08776A);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #51f3df, #347BF1);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #51f3df, #F35165);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #A7F9EF 0%, #51f3df 45%, #08776A 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F4FAFA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #81F6A3 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #6DB7F5 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #08776A 0%, transparent 65%), #51f3df;

Monochromatic scale

Palettes built from #51f3df

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.

#51f3df 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
ButtonsLinksFocus statesCharts
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 15.24:1.

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.

#51f3df, answered

What color is #51f3df?

#51f3df is a balanced electric cyan, closest to Turquoise (ΔE2000 4.3). It sits at 173° on the hue wheel with 87% saturation and 64% lightness, which reads as cool.

What is the RGB value of #51f3df?

rgb(81, 243, 223) — 81 red, 243 green and 223 blue out of 255, or 31.8% / 95.3% / 87.5% by channel.

What is #51f3df in HSL and HSV?

hsl(173, 87%, 64%) and hsv(173, 67%, 95%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #51f3df a light or a dark color?

It is a light color. Relative luminance is 0.7118 and perceived brightness is 81%, so black text on it reaches 15.24:1.

Should I use black or white text on #51f3df?

Black. It scores 15.24:1 against #51f3df, versus 1.38:1 for white — AAA at any size.

Is #51f3df accessible on a white background?

#51f3df on white scores 1.38:1, which fails WCAG AA at every size. Darken it to #098374 to reach 4.5:1, or #076257 for 7:1.

What is the complementary color of #51f3df?

#F35165 sits directly opposite on the wheel. Softer options are the split-complements #F351B6 and #F38E51, which give the same contrast with far less vibration.

What colors go well with #51f3df?

For interface work: #F4FAFA as the surface, #C0EDE7 for borders, #4B9B91 for secondary text, #F74D8C as an accent and #08776A for hover and pressed states. For a palette, the analogous pair #51F38E and #51B6F3 stays calm, while #F35165 is the loudest partner.

What is #51f3df in CMYK for printing?

cmyk(67%, 0%, 8%, 5%). 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 #51f3df warm or cool?

Cool — it scores 84 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #51F3A4; nudged cooler, #4FCCF5.

Which Tailwind color is closest to #51f3df?

The teal family — its 500 step is #14b8a6, ΔE2000 14.4 away. That is a visible difference, so define #51f3df as a custom token rather than reaching for the built-in.

How do I use #51f3df in Tailwind CSS?

Inline it as an arbitrary value with bg-[#51f3df] or text-[#51f3df], 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 #51f3df with 50% opacity?

rgba(81, 243, 223, 0.5), or #51f3df80 in eight-digit hex. Over white that composites to #A8F9EF; over black, #297A70.

Is #51f3df a web-safe color?

No. The nearest web-safe colour is #66FFCC, ΔE2000 8.7 away. The palette only matters for legacy displays and some email clients now.

What does the color #51f3df 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 #51f3df?

The safest is same-hue elevation: linear-gradient(135deg, #8AF7EA, #51f3df 45%, #08776A). For more colour, a short hue run to #347BF1 keeps it rich without turning muddy.

Work with #51f3df in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #51f3df at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.