What color is #666BD3?

#666BD3 is a medium blue-violet. In RGB it is rgb(102, 107, 211), and in HSL hsl(237, 55%, 61%).

Is #666BD3 accessible as text?

On white, #666BD3 has a contrast ratio of 4.56:1 (passes WCAG AA for body text); on black it is 4.61:1 (passes). For text placed on #666BD3, use black for the best readability.

What is the closest Tailwind color to #666BD3?

The nearest Tailwind CSS token is indigo-500 (#615FFF).

What colors go well with #666BD3?

#666BD3 pairs cleanly with neutrals — cream, taupe, charcoal and cool grays — and with its complementary #D2CD65. In UI, a softer accent is often easier to use than the exact complement. Explore the harmonies, shades, tints and ready-made palettes for #666BD3 below.

Is #666BD3 good for buttons?

#666BD3 works for buttons; black text has the higher contrast, so prefer it for labels.

Is #666BD3 the same as CSS slateblue?

No — #666BD3 is not the CSS named color slateblue, but slateblue (#6A5ACD) is the closest CSS named color.

#666BD3 Color — HEX, RGB, HSL, Palette & Shades

Palettes built on #666BD3

Not just a swatch — here's how #666BD3 works with other colors. Named schemes with #666BD3 in its natural role, and a note on why the supporting colors balance it.

Coastal Morning Lead · 5 colors

Lead #666BD3 Accent #A5C4C2 Surface #EAD5BF Secondary #9AA0A1 Anchor #22344A

Slate Blue opens this coastal palette with sea-glass and warm sand alongside it, grounded by driftwood grey and a deep-navy anchor.

Vintage Leather Lead · 5 colors

Lead #666BD3 Secondary #7F4534 Surface #EED7C2 Accent #365247 Anchor #582239

Slate Blue plays the worn-leather lead, deepened by saddle brown and an oxblood anchor, softened by aged cream and cooled by a muted forest green.

Modern Café Dominant · 5 colors

Dominant #666BD3 Anchor #3B2923 Surface #F3E1D2 Accent #769F7B Secondary #3C3734

Slate Blue anchors this café scheme as the warm mid-tone, lifted by latte cream and a muted sage accent and grounded by espresso brown and a warm charcoal.

Berry & Cream Lead · 5 colors

Lead #666BD3 Surface #F6E5D8 Anchor #5B2142 Accent #E5C2C9 Secondary #322B2F

Slate Blue sits between cream and a deep berry here, softened by a blush accent and grounded by charcoal.

Minimal Editorial Surface · 5 colors

Surface #F8F4EF Accent #666BD3 Secondary #9BA0C6 Support #9D9088 Ink #18140F

Slate Blue is the single accent in this high-contrast editorial system — set on near-white paper against near-black ink, with a warm grey and a desaturated tint of Slate Blue carrying the quiet middle.

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Color Lab

How #666BD3 actually behaves in design work — read from its OKLCH lightness, chroma and hue, not just its raw numbers. Ten signals to help you decide where this color earns its place.

Warmth 19/100

Cool

Reads cool and recessive — calming, technical, good for trust-led UI.

Softness 41/100

Moderate

Middle-weight — neither delicate nor heavy.

Depth 44/100

Moderate

Mid depth — usable as an accent or a muted ground.

Naturalness 0/100

Very low

Reads engineered rather than organic — synthetic, digital.

Vintage feel 41/100

Moderate

A faint retro warmth without tipping into sepia.

Luxury 48/100

Moderate

Understated — leans refined without going austere.

Brand distinctiveness 42/100

Moderate

Recognisable but shares space with nearby hues.

UI accent fit 95/100

Very high

Strong interactive accent — visible and can carry a legible label.

Surface fit 15/100

Very low

Too saturated or mid-toned for big areas — keep it to accents.

Print safety 76/100

High

Reproduces faithfully in CMYK — safe for packaging and print.

Pairs with #666BD3

For UI

For branding

For interior

For fashion

People also use #666BD3 with

Maya Blue Amethyst Citrine Gainsboro Prussian Blue

UI roles & guardrails

Primary action Safe as a filled button with white label. AA

Body text Passes on white at 16px and above. Pass

Large display Fine for headings 24px+ on white. Pass

Background Pair with white text at 4.6:1. Use

Subtle surface Use #E3E4F3 for cards and hover fills. Tint 80

Avoid beside #8465D2 — the hue gap is too small to read as intentional. Clash

In real applications

Not a swatch to memorise — a color to build with. Here is #666BD3 at work across the surfaces designers actually ship.

Website / UI

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Dashboard

Revenue

$48.2k ▲ 12%

Brand

AVELINE

Studio

Poster

Nov 14 · 8PM

NIGHT
MARKET

Packaging

BLOOM

Botanical Wash

250 ml

Interior

Every model

Export

:root {
  --color-base: #666BD3;
  --color-base-rgb: 102 107 211;
  --color-base-oklch: oklch(57.5% 0.157 278.2);
  --color-50: #F3F3FC;
  --color-100: #DFE0F6;
  --color-200: #C0C2ED;
  --color-300: #9498DB;
  --color-400: #6B70C7;
  --color-500: #4A4FAB;
  --color-600: #3F4283;
  --color-700: #31335E;
  --color-800: #23253E;
  --color-900: #171826;
  --color-on-base: #141310;
}

// tailwind.config.js
colors: {
  slate-blue: {
    50: '#F3F3FC',
    100: '#DFE0F6',
    200: '#C0C2ED',
    300: '#9498DB',
    400: '#6B70C7',
    500: '#4A4FAB',
    600: '#3F4283',
    700: '#31335E',
    800: '#23253E',
    900: '#171826',
  },
}

$base: #666BD3;
$base-ink: #141310;
$base-50: #F3F3FC;
$base-100: #DFE0F6;
$base-200: #C0C2ED;
$base-300: #9498DB;
$base-400: #6B70C7;
$base-500: #4A4FAB;
$base-600: #3F4283;
$base-700: #31335E;
$base-800: #23253E;
$base-900: #171826;
$base-hover: #383FC1;
$base-subtle: #D5D6EE;

{
    "color": {
        "base": {
            "value": "#666BD3",
            "type": "color"
        },
        "onBase": {
            "value": "#141310",
            "type": "color"
        },
        "scale": {
            "50": {
                "value": "#F3F3FC",
                "type": "color"
            },
            "100": {
                "value": "#DFE0F6",
                "type": "color"
            },
            "200": {
                "value": "#C0C2ED",
                "type": "color"
            },
            "300": {
                "value": "#9498DB",
                "type": "color"
            },
            "400": {
                "value": "#6B70C7",
                "type": "color"
            },
            "500": {
                "value": "#4A4FAB",
                "type": "color"
            },
            "600": {
                "value": "#3F4283",
                "type": "color"
            },
            "700": {
                "value": "#31335E",
                "type": "color"
            },
            "800": {
                "value": "#23253E",
                "type": "color"
            },
            "900": {
                "value": "#171826",
                "type": "color"
            }
        }
    }
}

Palettes built on #666BD3

Color Lab

Pairs with #666BD3

UI roles & guardrails

In real applications

Scales

Every model

Export