What color is #666FC4?

#666FC4 is a medium blue-violet. In RGB it is rgb(102, 111, 196), and in HSL hsl(234, 44%, 58%).

Is #666FC4 accessible as text?

On white, #666FC4 has a contrast ratio of 4.53:1 (passes WCAG AA for body text); on black it is 4.64:1 (passes). For text placed on #666FC4, use black for the best readability.

What is the closest Tailwind color to #666FC4?

The nearest Tailwind CSS token is sky-600 (#0084D1).

What colors go well with #666FC4?

#666FC4 pairs cleanly with neutrals — cream, taupe, charcoal and cool grays — and with its complementary #C3BA65. In UI, a softer accent is often easier to use than the exact complement. Explore the harmonies, shades, tints and ready-made palettes for #666FC4 below.

Is #666FC4 good for buttons?

#666FC4 works for buttons; black text has the higher contrast, so prefer it for labels.

Is #666FC4 the same as CSS slateblue?

No — #666FC4 is not the CSS named color slateblue, but slateblue (#6A5ACD) is the closest CSS named color.

#666FC4 Color — HEX, RGB, HSL, Palette & Shades

Palettes built on #666FC4

Not just a swatch — here's how #666FC4 works with other colors. Named schemes with #666FC4 in its natural role, and a note on why the supporting colors balance it.

Coastal Morning Lead · 5 colors

Lead #666FC4 Accent #A5C4C2 Surface #EAD5BF Secondary #9AA0A1 Anchor #22344A

Very Peri 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 #666FC4 Secondary #7F4534 Surface #EED7C2 Accent #365247 Anchor #582239

Very Peri 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 #666FC4 Anchor #3B2923 Surface #F3E1D2 Accent #769F7B Secondary #3C3734

Very Peri 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 #666FC4 Surface #F6E5D8 Anchor #5B2142 Accent #E5C2C9 Secondary #322B2F

Very Peri 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 #666FC4 Secondary #9BA1C0 Support #9D9088 Ink #18140F

Very Peri 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 Very Peri carrying the quiet middle.

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Color Lab

How #666FC4 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 24/100

Cool

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

Softness 45/100

Moderate

Middle-weight — neither delicate nor heavy.

Depth 43/100

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 50/100

Moderate

A faint retro warmth without tipping into sepia.

Luxury 49/100

Moderate

Understated — leans refined without going austere.

Brand distinctiveness 35/100

Low

Recognisable but shares space with nearby hues.

UI accent fit 96/100

Very high

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

Surface fit 20/100

Very low

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

Print safety 80/100

High

Reproduces faithfully in CMYK — safe for packaging and print.

Pairs with #666FC4

For UI

For branding

For interior

For fashion

People also use #666FC4 with

Iceberg Amethyst Dark Khaki 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 4.5:1. Use

Subtle surface Use #E3E4F0 for cards and hover fills. Tint 80

Avoid beside #7B65C3 — 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 #666FC4 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: #666FC4;
  --color-base-rgb: 102 111 196;
  --color-base-oklch: oklch(57.4% 0.130 276.9);
  --color-50: #F4F4FB;
  --color-100: #E1E3F4;
  --color-200: #C4C8E8;
  --color-300: #9BA1D4;
  --color-400: #757CBD;
  --color-500: #545BA1;
  --color-600: #464B7C;
  --color-700: #363959;
  --color-800: #26283B;
  --color-900: #191A25;
  --color-on-base: #141310;
}

// tailwind.config.js
colors: {
  very-peri: {
    50: '#F4F4FB',
    100: '#E1E3F4',
    200: '#C4C8E8',
    300: '#9BA1D4',
    400: '#757CBD',
    500: '#545BA1',
    600: '#464B7C',
    700: '#363959',
    800: '#26283B',
    900: '#191A25',
  },
}

$base: #666FC4;
$base-ink: #141310;
$base-50: #F4F4FB;
$base-100: #E1E3F4;
$base-200: #C4C8E8;
$base-300: #9BA1D4;
$base-400: #757CBD;
$base-500: #545BA1;
$base-600: #464B7C;
$base-700: #363959;
$base-800: #26283B;
$base-900: #191A25;
$base-hover: #424DAA;
$base-subtle: #D4D6EA;

{
    "color": {
        "base": {
            "value": "#666FC4",
            "type": "color"
        },
        "onBase": {
            "value": "#141310",
            "type": "color"
        },
        "scale": {
            "50": {
                "value": "#F4F4FB",
                "type": "color"
            },
            "100": {
                "value": "#E1E3F4",
                "type": "color"
            },
            "200": {
                "value": "#C4C8E8",
                "type": "color"
            },
            "300": {
                "value": "#9BA1D4",
                "type": "color"
            },
            "400": {
                "value": "#757CBD",
                "type": "color"
            },
            "500": {
                "value": "#545BA1",
                "type": "color"
            },
            "600": {
                "value": "#464B7C",
                "type": "color"
            },
            "700": {
                "value": "#363959",
                "type": "color"
            },
            "800": {
                "value": "#26283B",
                "type": "color"
            },
            "900": {
                "value": "#191A25",
                "type": "color"
            }
        }
    }
}

Palettes built on #666FC4

Color Lab

Pairs with #666FC4

UI roles & guardrails

In real applications

Scales

Every model

Export