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blue · cool

#100fef

a balanced, electric blue · cool · closest name: Blue

Token name suggestion: Atlas Sapphire

RGB
16, 15, 239
HSL
240°, 88%, 50%
CMYK
93, 94, 0, 6
Luminance
0.0668

#100fef is a balanced electric blue, 240° on the wheel and 83/100 on the cool side. Put white text on it (8.99:1). As text it scores 8.99:1 on white — safe at any size. Nearest name is Blue, nearest Tailwind family is indigo.

hsl(240 88% 50%)rgb(16 15 239)Base step 600AAA inkCool

At a glance

Every number on this page in one read: what #100fef is made of, how bright it looks, and which way it leans.

Hex
#100fef
Hue
240°
blue
Saturation
88%
electric
Lightness
50%
balanced
Brightness
94%
HSV value
Perceived
32%
weighted brightness
Luminance
0.0668
WCAG relative
Temperature
Cool
83/100 cool
Color family
Blue
Tone
Electric
Best ink
White
8.99:1
Closest name
Blue
ΔE2000 1.7
Chroma
124.5
LCH, 0–130ish
OKLCH L
0.438
perceptual lightness
Tailwind
indigo
500 · ΔE 19
Web-safe
#0000FF
nearest of 216
Where it sits
Hue240° of 360°
Saturation88%
Lightness50%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #100fef.

Temperature
Warm ← → Cool83% 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%
Green5%
Blue93%

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

Every format

HEX#100fef
HEX (8-digit)#100fefff
RGBrgb(16, 15, 239)
RGBArgba(16, 15, 239, 1)
HSLhsl(240, 88%, 50%)
HSV / HSBhsv(240, 94%, 94%)
HWBhwb(240 6% 6%)
CMYKcmyk(93%, 94%, 0%, 6%)
LABlab(31.1 73.0 -100.9)
LCHlch(31.1 124.5 305.9)
OKLCHoklch(0.438 0.292 265.4)
XYZ (D65)xyz(15.96, 6.68, 82.09)
Decimal1052655
Display P3color(display-p3 0.063 0.059 0.937)
Web-safe#0000FF

Copy-ready code

every platformclick to select
/* CSS */
color: #100fef;
background-color: #100fef;
/* CSS custom property */
--brand: #100fef;
/* Tailwind (arbitrary) */
class="text-[#100fef] bg-[#100fef]"
/* SCSS */
$brand: #100fef;
/* SwiftUI */
Color(red: 0.063, green: 0.059, blue: 0.937)
/* UIKit */
UIColor(red: 0.063, green: 0.059, blue: 0.937, alpha: 1)
/* Android XML */
<color name="brand">#100FEF</color>
/* Android Compose */
Color(0xFF100FEF)
/* Flutter */
Color(0xFF100FEF)
/* Python / OpenCV (BGR) */
(239, 15, 16)
/* Python / PIL (RGB) */
(16, 15, 239)
/* Java AWT */
new Color(16, 15, 239)
/* .NET */
Color.FromArgb(255, 16, 15, 239)
/* OpenGL / Unity (0–1) */
(0.0627f, 0.0588f, 0.9373f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{16,15,239}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #100fef 85%, white);
border-color: color-mix(in oklab, #100fef 40%, transparent);
/* theme-aware in one line */
color: light-dark(#080878, #D3D3EE);
/* relative colour syntax */
--hover: hsl(from #100fef 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: #F2F2FD;
  --brand-100: #E5E5FA;
  --brand-200: #C4C4F8;
  --brand-300: #9695F8;
  --brand-400: #6161F5;
  --brand-500: #2D2CF2;
  --brand-600: #100fef;
  --brand-700: #0D0CC0;
  --brand-800: #0A0A9A;
  --brand-900: #0C0C6F;
  --brand-950: #080745;
  --brand: #100fef;
  --brand-ink: #ffffff;
  --brand-surface: #F4F4FA;
  --brand-border: #C0C0ED;
  --brand-hover: #0E0DCD;
  --brand-pressed: #0C0BAC;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #141424;
    --brand-ink: #D3D3EE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F2F2FD',
        100: '#E5E5FA',
        200: '#C4C4F8',
        300: '#9695F8',
        400: '#6161F5',
        500: '#2D2CF2',
        600: '#100fef',
        700: '#0D0CC0',
        800: '#0A0A9A',
        900: '#0C0C6F',
        950: '#080745',
        DEFAULT: '#100fef',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F2F2FD,
  '100': #E5E5FA,
  '200': #C4C4F8,
  '300': #9695F8,
  '400': #6161F5,
  '500': #2D2CF2,
  '600': #100fef,
  '700': #0D0CC0,
  '800': #0A0A9A,
  '900': #0C0C6F,
  '950': #080745,
);
$brand-base: #100fef;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F2F2FD", "$type": "color" },
      "100": { "$value": "#E5E5FA", "$type": "color" },
      "200": { "$value": "#C4C4F8", "$type": "color" },
      "300": { "$value": "#9695F8", "$type": "color" },
      "400": { "$value": "#6161F5", "$type": "color" },
      "500": { "$value": "#2D2CF2", "$type": "color" },
      "600": { "$value": "#100fef", "$type": "color" },
      "700": { "$value": "#0D0CC0", "$type": "color" },
      "800": { "$value": "#0A0A9A", "$type": "color" },
      "900": { "$value": "#0C0C6F", "$type": "color" },
      "950": { "$value": "#080745", "$type": "color" }
    },
    "brandInk": { "$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 #100fef · 8.99:1
Use #ffffffAAA at every size.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 8.99:1 · recommended
AA pass · AA large pass · AAA pass
Aa
Black text · 2.34:1
AA fail · AA large fail · AAA fail
Reading the other direction: #100fef as text scores 8.99:1 on white and 2.34:1 on black.
Best tinted ink on it, if plain black or white feels flat: #E7E7FD at 7.38:1.

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
#100fef · 8.99:1
AA on whitealready passes
#100fef
The quick fox
#100fef · 8.99:1
AAA on whitealready passes
#100fef
The quick fox
#6564F5 · 4.69:1
AA on black+18% L
#6564F5
The quick fox
#8B8BF8 · 7.15:1
AAA on black+26% L
#8B8BF8

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #100FEF 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
#100fef on white: 8.99:1
AA ✓ pass · AA-large · AAA
Aa
#100fef on black: 2.34:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #100fef as text on that neutral, and that neutral as text on #100fef.

NeutralRatioBoth directions
White8.99:1AaAa
Slate 508.59:1AaAa
Slate 1008.20:1AaAa
Slate 2007.29:1AaAa
Slate 3006.05:1AaAa
Slate 4003.50:1AaAa
Slate 5001.89:1AaAa
Slate 6001.19:1AaAa
Slate 7001.15:1AaAa
Slate 8001.63:1AaAa
Slate 9001.99:1AaAa
Black2.34:1AaAa
Colour vision deficiency
true color
protanopia · #0055F4
deuteranopia · #003CEC
tritanopia · #00658D

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. #100fef 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.

#F2F2FD
#E5E5FA
#C4C4F8
#9695F8
#6161F5
#2D2CF2
#100fef
#0D0CC0
#0A0A9A
#0C0C6F
#080745
Base = 600Lightest = 50 · #F2F2FDDarkest = 950 · #080745Text step on white = 400
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 0.073 265.4);
  --brand-100: oklch(0.94 0.117 265.4);
  --brand-200: oklch(0.88 0.175 265.4);
  --brand-300: oklch(0.80 0.228 265.4);
  --brand-400: oklch(0.72 0.269 265.4);
  --brand-500: oklch(0.64 0.292 265.4);
  --brand-600: oklch(0.56 0.292 265.4);
  --brand-700: oklch(0.48 0.275 265.4);
  --brand-800: oklch(0.40 0.246 265.4);
  --brand-900: oklch(0.32 0.205 265.4);
  --brand-950: oklch(0.24 0.161 265.4);
}

Colors that work with #100fef

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#F4F4FA
Tinted page background
Border#C0C0ED
Hairlines and dividers
Muted text#4B4B9B
Captions on the surface
Accent#C49608
Second voice, not a rival
Dark variant#080878
Hover, pressed, headers
Light variant#E7E7FD
Selected rows, tints
Dark surface#141424
Dark-mode background
Hover#0E0DCD
One step down in lightness
Pressed#0C0BAC
Two steps down
Disabled#A7A7C7
Chroma pulled out
Focus ring#1716FD
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 #100fef

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
  • Text on black or near-black surfaces
  • 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.

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

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

Reads as
  • FormalityLow
  • EnergyHigh
  • Weight50/100
  • 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#EEEF0F
Analogous left#0F7EEF
Analogous right#800FEF
Split-complement 1#EF800F
Split-complement 2#7EEF0F
Triadic 1#EF100F
Triadic 2#0FEF10
Tetradic#EF0F7E
On the wheel
Base+30°−30°+120°+240°+180°240°

#100fef sits at 240°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red6.3%
Green5.9%
Blue93.7%
R · 0–255
16
0x10
G · 0–255
15
0x0f
B · 0–255
239
0xef

CMYK percentages

Cyan93.3%
Magenta93.7%
Yellow0.0%
Key (black)6.3%

Total ink coverage is 193%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#100fef text on a black background

contrast 2.34:1

Card sample

#100fef text on a white background

contrast 8.99:1

Card sample

#100fef on grey

8.20:1

#100fef on its own surface

8.20:1

#100fef on its dark surface

2.02:1

CSS3 live lab

Text font color

The quick brown fox

color: #100fef;
Background color
Panel with #100fef background
background-color: #100fef;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #100fef;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(16, 15, 239, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(16, 15, 239, 0.45);
Border & gradient
Gradient panel
border: 3px solid #100fef;
background: linear-gradient(135deg, #100fef, #A50FEF);
Gradient text

Gradient headline

background: linear-gradient(90deg, #100fef, #DD0FEF);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #100fef;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #100fef;
caret-color: #100fef;
Left rule
Pull quote or callout
border-left: 4px solid #100fef;
Ring + tint
Selected chip
background: #E7E7FD;
box-shadow: inset 0 0 0 2px #100fef;
Conic badge
68%
background: conic-gradient(#100fef 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #100fef 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(16, 15, 239, 0.5)
rgb(16 15 239 / 50%)
#100fef80
hsl(240 88% 50% / 50%)
color-mix(in srgb, #100fef 50%, transparent)
Alpha8-digit hexFlat on white
10%#100fef1a#E7E7FD
20%#100fef33#CFCFFC
40%#100fef66#9F9FF9
60%#100fef99#706FF5
80%#100fefcc#403FF2

Gradients from #100fef

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, #4948F4, #100fef 45%, #080878);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #100fef, #A20DD2);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #100fef, #EEEF0F);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #6564F5 0%, #100fef 45%, #080878 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F4F4FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #3EA7F3 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #A02BF2 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #080878 0%, transparent 65%), #100fef;

Monochromatic scale

Palettes built from #100fef

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.

#100fef 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

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

Too dim on dark surfaces at 2.34:1 — lift it to #6564F5 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.

#100fef, answered

What color is #100fef?

#100fef is a balanced electric blue, closest to Blue (ΔE2000 1.7). It sits at 240° on the hue wheel with 88% saturation and 50% lightness, which reads as cool.

What is the RGB value of #100fef?

rgb(16, 15, 239) — 16 red, 15 green and 239 blue out of 255, or 6.3% / 5.9% / 93.7% by channel.

What is #100fef in HSL and HSV?

hsl(240, 88%, 50%) and hsv(240, 94%, 94%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #100fef a light or a dark color?

It is a dark color. Relative luminance is 0.0668 and perceived brightness is 32%, so white text on it reaches 8.99:1.

Should I use black or white text on #100fef?

White. It scores 8.99:1 against #100fef, versus 2.34:1 for black — AAA at any size.

Is #100fef accessible on a white background?

#100fef on white scores 8.99:1, which clears AAA at every size.

What is the complementary color of #100fef?

#EEEF0F sits directly opposite on the wheel. Softer options are the split-complements #EF800F and #7EEF0F, which give the same contrast with far less vibration.

What colors go well with #100fef?

For interface work: #F4F4FA as the surface, #C0C0ED for borders, #4B4B9B for secondary text, #C49608 as an accent and #080878 for hover and pressed states. For a palette, the analogous pair #0F7EEF and #800FEF stays calm, while #EEEF0F is the loudest partner.

What is #100fef in CMYK for printing?

cmyk(93%, 94%, 0%, 6%). 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 #100fef warm or cool?

Cool — it scores 83 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #620FEF; nudged cooler, #0C3EF2.

Which Tailwind color is closest to #100fef?

The indigo family — its 500 step is #6366f1, ΔE2000 19 away. That is a visible difference, so define #100fef as a custom token rather than reaching for the built-in.

How do I use #100fef in Tailwind CSS?

Inline it as an arbitrary value with bg-[#100fef] or text-[#100fef], 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 #100fef with 50% opacity?

rgba(16, 15, 239, 0.5), or #100fef80 in eight-digit hex. Over white that composites to #8887F7; over black, #080878.

Is #100fef a web-safe color?

No. The nearest web-safe colour is #0000FF, ΔE2000 1.7 away. The palette only matters for legacy displays and some email clients now.

What does the color #100fef 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 #100fef?

The safest is same-hue elevation: linear-gradient(135deg, #4948F4, #100fef 45%, #080878). For more colour, a short hue run to #A20DD2 keeps it rich without turning muddy.

Work with #100fef in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #100fef at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.