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blue · cool

#665acb

a balanced, vivid blue · cool · “Slate Blue”

Token name suggestion: Atlas Denim

RGB
102, 90, 203
HSL
246°, 52%, 58%
CMYK
50, 56, 0, 20
Luminance
0.1445

#665acb is a balanced vivid blue, 246° on the wheel and 80/100 on the cool side. Put white text on it (5.40:1). As text it scores 5.40:1 on white — safe at any size. Nearest name is Slate Blue, nearest Tailwind family is indigo.

hsl(246 52% 58%)rgb(102 90 203)Base step 500AA inkCool

At a glance

Every number on this page in one read: what #665acb is made of, how bright it looks, and which way it leans.

Hex
#665acb
Hue
246°
blue
Saturation
52%
vivid
Lightness
58%
balanced
Brightness
80%
HSV value
Perceived
44%
weighted brightness
Luminance
0.1445
WCAG relative
Temperature
Cool
80/100 cool
Color family
Blue
Tone
Vivid
Best ink
White
5.40:1
Closest name
Slate Blue
ΔE2000 0.8
Chroma
67.0
LCH, 0–130ish
OKLCH L
0.539
perceptual lightness
Tailwind
indigo
500 · ΔE 6.7
Web-safe
#6666CC
nearest of 216
Where it sits
Hue246° of 360°
Saturation52%
Lightness58%
Saturation × lightness field

Left edge is grey, right edge is full chroma; top is white, bottom is black. The dot is #665acb.

Temperature
Warm ← → Cool80% 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
Red20%
Green51%
Blue30%

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

Every format

HEX#665acb
HEX (8-digit)#665acbff
RGBrgb(102, 90, 203)
RGBArgba(102, 90, 203, 1)
HSLhsl(246, 52%, 58%)
HSV / HSBhsv(246, 56%, 80%)
HWBhwb(246 35% 20%)
CMYKcmyk(50%, 56%, 0%, 20%)
LABlab(44.9 34.6 -57.4)
LCHlch(44.9 67.0 301.1)
OKLCHoklch(0.539 0.169 284.0)
XYZ (D65)xyz(19.91, 14.45, 58.23)
Decimal6707915
Display P3color(display-p3 0.400 0.353 0.796)
Web-safe#6666CC

Copy-ready code

every platformclick to select
/* CSS */
color: #665acb;
background-color: #665acb;
/* CSS custom property */
--brand: #665acb;
/* Tailwind (arbitrary) */
class="text-[#665acb] bg-[#665acb]"
/* SCSS */
$brand: #665acb;
/* SwiftUI */
Color(red: 0.400, green: 0.353, blue: 0.796)
/* UIKit */
UIColor(red: 0.400, green: 0.353, blue: 0.796, alpha: 1)
/* Android XML */
<color name="brand">#665ACB</color>
/* Android Compose */
Color(0xFF665ACB)
/* Flutter */
Color(0xFF665ACB)
/* Python / OpenCV (BGR) */
(203, 90, 102)
/* Python / PIL (RGB) */
(102, 90, 203)
/* Java AWT */
new Color(102, 90, 203)
/* .NET */
Color.FromArgb(255, 102, 90, 203)
/* OpenGL / Unity (0–1) */
(0.4000f, 0.3529f, 0.7961f, 1f)
/* LaTeX */
\definecolor{brand}{RGB}{102,90,203}
modern cssclick to select
/* mix without leaving CSS */
background: color-mix(in oklab, #665acb 85%, white);
border-color: color-mix(in oklab, #665acb 40%, transparent);
/* theme-aware in one line */
color: light-dark(#261F61, #D6D3EE);
/* relative colour syntax */
--hover: hsl(from #665acb 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: #F5F4FA;
  --brand-100: #EBE9F6;
  --brand-200: #D2CFED;
  --brand-300: #B0AAE4;
  --brand-400: #887FD7;
  --brand-500: #665acb;
  --brand-600: #483BBA;
  --brand-700: #3C319B;
  --brand-800: #30277C;
  --brand-900: #26205B;
  --brand-950: #181439;
  --brand: #665acb;
  --brand-ink: #ffffff;
  --brand-surface: #F5F4FA;
  --brand-border: #C5C1EB;
  --brand-hover: #4D3FC3;
  --brand-pressed: #4135A9;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand-surface: #151424;
    --brand-ink: #D6D3EE;
  }
}
tailwind.config.jsclick to select
theme: {
  extend: {
    colors: {
      brand: {
        50: '#F5F4FA',
        100: '#EBE9F6',
        200: '#D2CFED',
        300: '#B0AAE4',
        400: '#887FD7',
        500: '#665acb',
        600: '#483BBA',
        700: '#3C319B',
        800: '#30277C',
        900: '#26205B',
        950: '#181439',
        DEFAULT: '#665acb',
      },
    },
  },
}
scss mapclick to select
$brand: (
  '50': #F5F4FA,
  '100': #EBE9F6,
  '200': #D2CFED,
  '300': #B0AAE4,
  '400': #887FD7,
  '500': #665acb,
  '600': #483BBA,
  '700': #3C319B,
  '800': #30277C,
  '900': #26205B,
  '950': #181439,
);
$brand-base: #665acb;
$brand-ink: #ffffff;

@function brand($step) { @return map-get($brand, $step); }
w3c design tokens (json)click to select
{
  "color": {
    "brand": {
      "50": { "$value": "#F5F4FA", "$type": "color" },
      "100": { "$value": "#EBE9F6", "$type": "color" },
      "200": { "$value": "#D2CFED", "$type": "color" },
      "300": { "$value": "#B0AAE4", "$type": "color" },
      "400": { "$value": "#887FD7", "$type": "color" },
      "500": { "$value": "#665acb", "$type": "color" },
      "600": { "$value": "#483BBA", "$type": "color" },
      "700": { "$value": "#3C319B", "$type": "color" },
      "800": { "$value": "#30277C", "$type": "color" },
      "900": { "$value": "#26205B", "$type": "color" },
      "950": { "$value": "#181439", "$type": "color" }
    },
    "brandInk": { "$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 #665acb · 5.40:1
Use #ffffffAA at every size, AAA for large text only.
Aa
12px
Aa
16px
Aa
24px
Aa
White text · 5.40:1 · recommended
AA pass · AA large pass · AAA fail
Aa
Black text · 3.89:1
AA fail · AA large pass · AAA fail
Reading the other direction: #665acb as text scores 5.40:1 on white and 3.89:1 on black.
Best tinted ink on it, if plain black or white feels flat: #EDECF9 at 4.62:1.

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
#665acb · 5.40:1
AA on whitealready passes
#665acb
The quick fox
#5143C4 · 7.12:1
AAA on white−6% L
#5143C4
The quick fox
#7166CF · 4.50:1
AA on black+3% L
#7166CF
The quick fox
#958DDB · 7.11:1
AAA on black+13% L
#958DDB

Large text — 24px regular or 18.66px bold and above — only needs 3:1, so #665ACB 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
#665acb on white: 5.40:1
AA ✓ pass · AA-large · AAA
Aa
#665acb on black: 3.89:1
AA ✗ fail · AA-large · AAA
Against the neutral ladder

Contrast is symmetric, so each row covers both directions: #665acb as text on that neutral, and that neutral as text on #665acb.

NeutralRatioBoth directions
White5.40:1AaAa
Slate 505.16:1AaAa
Slate 1004.93:1AaAa
Slate 2004.38:1AaAa
Slate 3003.64:1AaAa
Slate 4002.11:1AaAa
Slate 5001.13:1AaAa
Slate 6001.40:1AaAa
Slate 7001.92:1AaAa
Slate 8002.71:1AaAa
Slate 9003.31:1AaAa
Black3.89:1AaAa
Colour vision deficiency
true color
protanopia · #116ECF
deuteranopia · #0267C9
tritanopia · #41738A

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. #665acb is pinned to step 500; the rest hold its hue and let saturation ease off at the extremes so the pale end never turns neon.

#F5F4FA
#EBE9F6
#D2CFED
#B0AAE4
#887FD7
#665acb
#483BBA
#3C319B
#30277C
#26205B
#181439
Base = 500Lightest = 50 · #F5F4FADarkest = 950 · #181439Text 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 0.042 284.0);
  --brand-100: oklch(0.94 0.068 284.0);
  --brand-200: oklch(0.88 0.101 284.0);
  --brand-300: oklch(0.80 0.132 284.0);
  --brand-400: oklch(0.72 0.155 284.0);
  --brand-500: oklch(0.64 0.169 284.0);
  --brand-600: oklch(0.56 0.169 284.0);
  --brand-700: oklch(0.48 0.159 284.0);
  --brand-800: oklch(0.40 0.142 284.0);
  --brand-900: oklch(0.32 0.118 284.0);
  --brand-950: oklch(0.24 0.093 284.0);
}

Colors that work with #665acb

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#F5F4FA
Tinted page background
Border#C5C1EB
Hairlines and dividers
Muted text#534B9B
Captions on the surface
Accent#9F8F2D
Second voice, not a rival
Dark variant#261F61
Hover, pressed, headers
Light variant#EDECF9
Selected rows, tints
Dark surface#151424
Dark-mode background
Hover#4D3FC3
One step down in lightness
Pressed#4135A9
Two steps down
Disabled#C2BFD6
Chroma pulled out
Focus ring#6D60DA
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 #665acb

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
  • Weight43/100
  • 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#BFCB5A
Analogous left#5A87CB
Analogous right#9F5ACB
Split-complement 1#CB9F5A
Split-complement 2#87CB5A
Triadic 1#CB665A
Triadic 2#5ACB66
Tetradic#CB5A87
On the wheel
Base+30°−30°+120°+240°+180°246°

#665acb sits at 246°. Every dot is a harmony position and links to its own page in the table alongside.

RGB percentages

Red40.0%
Green35.3%
Blue79.6%
R · 0–255
102
0x66
G · 0–255
90
0x5a
B · 0–255
203
0xcb

CMYK percentages

Cyan49.8%
Magenta55.7%
Yellow0.0%
Key (black)20.4%

Total ink coverage is 126%. Most commercial presses cap around 300% — above that, sheets stop drying properly.

Color previews

#665acb text on a black background

contrast 3.89:1

Card sample

#665acb text on a white background

contrast 5.40:1

Card sample

#665acb on grey

4.93:1

#665acb on its own surface

4.94:1

#665acb on its dark surface

3.36:1

CSS3 live lab

Text font color

The quick brown fox

color: #665acb;
Background color
Panel with #665acb background
background-color: #665acb;
Text shadow — hex

Glowing headline

text-shadow: 2px 2px 8px #665acb;
Text shadow — RGB

Soft neon halo

text-shadow: 0 0 14px rgba(102, 90, 203, 0.45);
Div box shadow
Elevated card
box-shadow: 0 12px 32px -8px rgba(102, 90, 203, 0.45);
Border & gradient
Gradient panel
border: 3px solid #665acb;
background: linear-gradient(135deg, #665acb, #B15ACB);
Gradient text

Gradient headline

background: linear-gradient(90deg, #665acb, #CB5AC8);
-webkit-background-clip: text;
color: transparent;
Focus ring
Focused control
outline: 2px solid #665acb;
outline-offset: 3px;
Underline & caret

Marked up text

text-decoration-color: #665acb;
caret-color: #665acb;
Left rule
Pull quote or callout
border-left: 4px solid #665acb;
Ring + tint
Selected chip
background: #EDECF9;
box-shadow: inset 0 0 0 2px #665acb;
Conic badge
68%
background: conic-gradient(#665acb 68%, #e2e8f0 0);

Transparency

What each alpha value actually composites to. The top row is #665acb 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(102, 90, 203, 0.5)
rgb(102 90 203 / 50%)
#665acb80
hsl(246 52% 58% / 50%)
color-mix(in srgb, #665acb 50%, transparent)
Alpha8-digit hexFlat on white
10%#665acb1a#F0EFFA
20%#665acb33#E0DEF5
40%#665acb66#C2BDEA
60%#665acb99#A39CE0
80%#665acbcc#857BD5

Gradients from #665acb

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, #9189DA, #665acb 45%, #261F61);
Duotone
A short hue run reads richer than a flat fill
background: linear-gradient(120deg, #665acb, #B143C4);
Complement sweep
Loud — keep it behind large type only
background: linear-gradient(90deg, #665acb, #BFCB5A);
Spotlight
Hero panels and app headers
background: radial-gradient(120% 120% at 20% 0%, #A7A0E1 0%, #665acb 45%, #261F61 100%);
Soft wash
Section backgrounds that stay readable
background: linear-gradient(180deg, #F5F4FA, #ffffff);
Mesh
Ambient background, no image weight
background: radial-gradient(60% 60% at 15% 20%, #81AAD7 0%, transparent 60%), radial-gradient(55% 55% at 85% 15%, #B471D2 0%, transparent 60%), radial-gradient(70% 70% at 50% 95%, #261F61 0%, transparent 65%), #665acb;

Monochromatic scale

Palettes built from #665acb

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.

#665acb 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 3.89:1 — lift it to #7166CF 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.

#665acb, answered

What color is #665acb?

#665acb is a balanced vivid blue — the CSS keyword Slate Blue. It sits at 246° on the hue wheel with 52% saturation and 58% lightness, which reads as cool.

What is the RGB value of #665acb?

rgb(102, 90, 203) — 102 red, 90 green and 203 blue out of 255, or 40% / 35.3% / 79.6% by channel.

What is #665acb in HSL and HSV?

hsl(246, 52%, 58%) and hsv(246, 56%, 80%). HSL is what CSS takes; HSV is what your design tool's picker shows, which is why the saturation numbers rarely match.

Is #665acb a light or a dark color?

It is a dark color. Relative luminance is 0.1445 and perceived brightness is 44%, so white text on it reaches 5.40:1.

Should I use black or white text on #665acb?

White. It scores 5.40:1 against #665acb, versus 3.89:1 for black — AA at any size.

Is #665acb accessible on a white background?

#665acb on white scores 5.40:1, which clears AA at every size but not AAA.

What is the complementary color of #665acb?

#BFCB5A sits directly opposite on the wheel. Softer options are the split-complements #CB9F5A and #87CB5A, which give the same contrast with far less vibration.

What colors go well with #665acb?

For interface work: #F5F4FA as the surface, #C5C1EB for borders, #534B9B for secondary text, #9F8F2D as an accent and #261F61 for hover and pressed states. For a palette, the analogous pair #5A87CB and #9F5ACB stays calm, while #BFCB5A is the loudest partner.

What is #665acb in CMYK for printing?

cmyk(50%, 56%, 0%, 20%). This is a screen-to-ink approximation — ask your printer for a proof before committing to a run.

Is #665acb warm or cool?

Cool — it scores 80 on a scale where 0 is the warmest orange and 100 the coolest azure. Nudged warmer it becomes #905ACB; nudged cooler, #5876CD.

Which Tailwind color is closest to #665acb?

The indigo family — its 500 step is #6366f1, ΔE2000 6.7 away. That is a visible difference, so define #665acb as a custom token rather than reaching for the built-in.

How do I use #665acb in Tailwind CSS?

Inline it as an arbitrary value with bg-[#665acb] or text-[#665acb], 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 #665acb with 50% opacity?

rgba(102, 90, 203, 0.5), or #665acb80 in eight-digit hex. Over white that composites to #B3ADE5; over black, #332D66.

Is #665acb a web-safe color?

No. The nearest web-safe colour is #6666CC, ΔE2000 4 away. The palette only matters for legacy displays and some email clients now.

What does the color #665acb 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 #665acb?

The safest is same-hue elevation: linear-gradient(135deg, #9189DA, #665acb 45%, #261F61). For more colour, a short hue run to #B143C4 keeps it rich without turning muddy.

Work with #665acb in the Color Lab

Every tool opens with this colour already loaded.

Every value on this page is computed from #665acb at request time — conversions, contrast ratios and ΔE distances are calculated, never looked up.