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blue · cool

#042df2

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

Token name suggestion: Signal Cobalt

RGB
4, 45, 242
HSL
230°, 97%, 48%
CMYK
98, 81, 0, 5
Luminance
0.0831

#042df2 is a balanced electric blue, 230° on the wheel and 89/100 on the cool side. Put white text on it (7.89:1). As text it scores 7.89:1 on white — safe at any size. Nearest name is Blue, nearest Tailwind family is indigo.

hsl(230 97% 48%)rgb(4 45 242)Base step 600AAA inkCool

At a glance

Every number on this page in one read: what #042df2 is made of, how bright it looks, and which way it leans.

Hex
#042df2
Hue
230°
blue
Saturation
97%
electric
Lightness
48%
balanced
Brightness
95%
HSV value
Perceived
35%
weighted brightness
Luminance
0.0831
WCAG relative
Temperature
Cool
89/100 cool
Color family
Blue
Tone
Electric
Best ink
White
7.89:1
Closest name
Blue
ΔE2000 4.1
Chroma
115.7
LCH, 0–130ish
OKLCH L
0.463
perceptual lightness
Tailwind
indigo
500 · ΔE 15.5
Web-safe
#0033FF
nearest of 216
Where it sits
Hue230° of 360°
Saturation97%
Lightness48%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #042df2.

Temperature
Warm ← → Cool89% 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
Red0%
Green23%
Blue77%

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

Every format

HEX#042df2
HEX (8-digit)#042df2ff
RGBrgb(4, 45, 242)
RGBArgba(4, 45, 242, 1)
HSLhsl(230, 97%, 48%)
HSV / HSBhsv(230, 98%, 95%)
HWBhwb(230 2% 5%)
CMYKcmyk(98%, 81%, 0%, 5%)
LABlab(34.6 63.6 -96.7)
LCHlch(34.6 115.7 303.3)
OKLCHoklch(0.463 0.281 264.4)
XYZ (D65)xyz(17.01, 8.31, 84.69)
Decimal273906
Display P3color(display-p3 0.016 0.176 0.949)
Web-safe#0033FF

Copy-ready code

every platformclick to select
/* CSS */
color: #042df2;
background-color: #042df2;
/* CSS custom property */
--brand: #042df2;
/* Tailwind (arbitrary) */
class="text-[#042df2] bg-[#042df2]"
/* SCSS */
$brand: #042df2;
/* SwiftUI */
Color(red: 0.016, green: 0.176, blue: 0.949)
/* UIKit */
UIColor(red: 0.016, green: 0.176, blue: 0.949, alpha: 1)
/* Android XML */
<color name="brand">#042DF2</color>
/* Android Compose */
Color(0xFF042DF2)
/* Flutter */
Color(0xFF042DF2)
/* Python / OpenCV (BGR) */
(242, 45, 4)
/* Python / PIL (RGB) */
(4, 45, 242)
/* Java AWT */
new Color(4, 45, 242)
/* .NET */
Color.FromArgb(255, 4, 45, 242)
/* OpenGL / Unity (0–1) */
(0.0157f, 0.1765f, 0.9490f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{4,45,242}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #042df2 85%, white);
border-color: color-mix(in oklab, #042df2 40%, transparent);
/* theme-aware in one line */
color: light-dark(#02177D, #D3D7EE);
/* relative colour syntax */
--hover: hsl(from #042df2 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: #F1F3FD;
  --brand-100: #E4E8FC;
  --brand-200: #C1CBFB;
  --brand-300: #91A3FD;
  --brand-400: #5975FC;
  --brand-500: #2248FB;
  --brand-600: #042df2;
  --brand-700: #0325C9;
  --brand-800: #031EA1;
  --brand-900: #071974;
  --brand-950: #041048;
  --brand: #042df2;
  --brand-ink: #ffffff;
  --brand-surface: #F4F5FA;
  --brand-border: #C0C7ED;
  --brand-hover: #0326CF;
  --brand-pressed: #0320AC;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #141724;
    --brand-ink: #D3D7EE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F1F3FD',
        100: '#E4E8FC',
        200: '#C1CBFB',
        300: '#91A3FD',
        400: '#5975FC',
        500: '#2248FB',
        600: '#042df2',
        700: '#0325C9',
        800: '#031EA1',
        900: '#071974',
        950: '#041048',
        DEFAULT: '#042df2',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F1F3FD,
  '100': #E4E8FC,
  '200': #C1CBFB,
  '300': #91A3FD,
  '400': #5975FC,
  '500': #2248FB,
  '600': #042df2,
  '700': #0325C9,
  '800': #031EA1,
  '900': #071974,
  '950': #041048,
);
$brand-base: #042df2;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F1F3FD", "$type": "color" },
      "100": { "$value": "#E4E8FC", "$type": "color" },
      "200": { "$value": "#C1CBFB", "$type": "color" },
      "300": { "$value": "#91A3FD", "$type": "color" },
      "400": { "$value": "#5975FC", "$type": "color" },
      "500": { "$value": "#2248FB", "$type": "color" },
      "600": { "$value": "#042df2", "$type": "color" },
      "700": { "$value": "#0325C9", "$type": "color" },
      "800": { "$value": "#031EA1", "$type": "color" },
      "900": { "$value": "#071974", "$type": "color" },
      "950": { "$value": "#041048", "$type": "color" }
    },
    "brandInk": { "$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 #042df2 · 7.89:1
Use #ffffffAAA at every size.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 7.89:1 · recommended
AA pass · AA large pass · AAA pass
Aa
Black text · 2.66:1
AA fail · AA large fail · AAA fail
Reading the other direction: #042df2 as text scores 7.89:1 on white and 2.66:1 on black.
Best tinted ink on it, if plain black or white feels flat: #E6EAFF at 6.60:1.

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
#042df2 · 7.89:1
AA on whitealready passes
#042df2
The quick fox
#042df2 · 7.89:1
AAA on whitealready passes
#042df2
The quick fox
#4666FC · 4.57:1
AA on black+15% L
#4666FC
The quick fox
#798FFD · 7.16:1
AAA on black+25% L
#798FFD

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #042DF2 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
#042df2 on white: 7.89:1
AA ✓ pass · AA-large · AAA
Aa
#042df2 on black: 2.66:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #042df2 as text on that neutral, and that neutral as text on #042df2.

NeutralRatioBoth directions
White7.89:1AaAa
Slate 507.54:1AaAa
Slate 1007.20:1AaAa
Slate 2006.40:1AaAa
Slate 3005.31:1AaAa
Slate 4003.08:1AaAa
Slate 5001.66:1AaAa
Slate 6001.04:1AaAa
Slate 7001.31:1AaAa
Slate 8001.85:1AaAa
Slate 9002.26:1AaAa
Black2.66:1AaAa
Colour vision deficiency
true color
protanopia · #005DF7
deuteranopia · #0045EF
tritanopia · #006E92

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. #042df2 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.

#F1F3FD
#E4E8FC
#C1CBFB
#91A3FD
#5975FC
#2248FB
#042df2
#0325C9
#031EA1
#071974
#041048
Base = 600Lightest = 50 · #F1F3FDDarkest = 950 · #041048Text 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 0.070 264.4);
  --brand-100: oklch(0.94 0.113 264.4);
  --brand-200: oklch(0.88 0.169 264.4);
  --brand-300: oklch(0.80 0.220 264.4);
  --brand-400: oklch(0.72 0.259 264.4);
  --brand-500: oklch(0.64 0.281 264.4);
  --brand-600: oklch(0.56 0.281 264.4);
  --brand-700: oklch(0.48 0.265 264.4);
  --brand-800: oklch(0.40 0.236 264.4);
  --brand-900: oklch(0.32 0.197 264.4);
  --brand-950: oklch(0.24 0.155 264.4);
}

Colors that work with #042df2

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#F4F5FA
Tinted page background
Border#C0C7ED
Hairlines and dividers
Muted text#4B589B
Captions on the surface
Accent#CC7600
Second voice, not a rival
Dark variant#02177D
Hover, pressed, headers
Light variant#E6EAFF
Selected rows, tints
Dark surface#141724
Dark-mode background
Hover#0326CF
One step down in lightness
Pressed#0320AC
Two steps down
Disabled#A2A8C4
Chroma pulled out
Focus ring#0B35FF
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 #042df2

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
  • Weight52/100
  • 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#F2C904
Analogous left#04A4F2
Analogous right#5204F2
Split-complement 1#F25204
Split-complement 2#A4F204
Triadic 1#F2042D
Triadic 2#2DF204
Tetradic#F204A4
On the wheel
Base+30°−30°+120°+240°+180°230°

#042df2 sits at 230°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red1.6%
Green17.6%
Blue94.9%
R · 0–255
4
0x04
G · 0–255
45
0x2d
B · 0–255
242
0xf2

CMYK percentages

Cyan98.3%
Magenta81.4%
Yellow0.0%
Key (black)5.1%

Total ink coverage is 185%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#042df2 text on a black background

contrast 2.66:1

Card sample

#042df2 text on a white background

contrast 7.89:1

Card sample

#042df2 on grey

7.20:1

#042df2 on its own surface

7.24:1

#042df2 on its dark surface

2.26:1

CSS3 live lab

Text font color

The quick brown fox

color: #042df2;
Background color
Panel with #042df2 background
background-color: #042df2;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #042df2;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(4, 45, 242, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(4, 45, 242, 0.45);
Border & gradient
Gradient panel
border: 3px solid #042df2;
background: linear-gradient(135deg, #042df2, #7A04F2);
Gradient text

Gradient headline

background: linear-gradient(90deg, #042df2, #B504F2);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #042df2;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #042df2;
caret-color: #042df2;
Left rule
Pull quote or callout
border-left: 4px solid #042df2;
Ring + tint
Selected chip
background: #E6EAFF;
box-shadow: inset 0 0 0 2px #042df2;
Conic badge
68%
background: conic-gradient(#042df2 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #042df2 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(4, 45, 242, 0.5)
rgb(4 45 242 / 50%)
#042df280
hsl(230 97% 48% / 50%)
color-mix(in srgb, #042df2 50%, transparent)
Alpha8-digit hexFlat on white
10%#042df21a#E6EAFE
20%#042df233#CDD5FC
40%#042df266#9BABFA
60%#042df299#6881F7
80%#042df2cc#3657F5

Gradients from #042df2

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, #3759FC, #042df2 45%, #02177D);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #042df2, #7C04D4);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #042df2, #F2C904);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #5572FC 0%, #042df2 45%, #02177D 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F4F5FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #2DC9FB 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #7619FB 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #02177D 0%, transparent 65%), #042df2;

Monochromatic scale

Palettes built from #042df2

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.

#042df2 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 2.66:1 — lift it to #4666FC 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.

#042df2, answered

What color is #042df2?

#042df2 is a balanced electric blue, closest to Blue (ΔE2000 4.1). It sits at 230° on the hue wheel with 97% saturation and 48% lightness, which reads as cool.

What is the RGB value of #042df2?

rgb(4, 45, 242) — 4 red, 45 green and 242 blue out of 255, or 1.6% / 17.6% / 94.9% by channel.

What is #042df2 in HSL and HSV?

hsl(230, 97%, 48%) and hsv(230, 98%, 95%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #042df2 a light or a dark color?

It is a dark color. Relative luminance is 0.0831 and perceived brightness is 35%, so white text on it reaches 7.89:1.

Should I use black or white text on #042df2?

White. It scores 7.89:1 against #042df2, versus 2.66:1 for black — AAA at any size.

Is #042df2 accessible on a white background?

#042df2 on white scores 7.89:1, which clears AAA at every size.

What is the complementary color of #042df2?

#F2C904 sits directly opposite on the wheel. Softer options are the split-complements #F25204 and #A4F204, which give the same contrast with far less vibration.

What colors go well with #042df2?

For interface work: #F4F5FA as the surface, #C0C7ED for borders, #4B589B for secondary text, #CC7600 as an accent and #02177D for hover and pressed states. For a palette, the analogous pair #04A4F2 and #5204F2 stays calm, while #F2C904 is the loudest partner.

What is #042df2 in CMYK for printing?

cmyk(98%, 81%, 0%, 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 #042df2 warm or cool?

Cool — it scores 89 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #3204F2; nudged cooler, #024CF4.

Which Tailwind color is closest to #042df2?

The indigo family — its 500 step is #6366f1, ΔE2000 15.5 away. That is a visible difference, so define #042df2 as a custom token rather than reaching for the built-in.

How do I use #042df2 in Tailwind CSS?

Inline it as an arbitrary value with bg-[#042df2] or text-[#042df2], 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 #042df2 with 50% opacity?

rgba(4, 45, 242, 0.5), or #042df280 in eight-digit hex. Over white that composites to #8296F9; over black, #021779.

Is #042df2 a web-safe color?

No. The nearest web-safe colour is #0033FF, ΔE2000 2.2 away. The palette only matters for legacy displays and some email clients now.

What does the color #042df2 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 #042df2?

The safest is same-hue elevation: linear-gradient(135deg, #3759FC, #042df2 45%, #02177D). For more colour, a short hue run to #7C04D4 keeps it rich without turning muddy.

Work with #042df2 in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #042df2 at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.