#666AC2
Closest named color: Dark Periwinkle (#665FD1). oklch(56.3% 0.134 279.2), rgb(102, 106, 194).
Aa
White text reads best on this color (4.76:1).
About this color
#666AC2 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 56%, its chroma 0.134 and its hue 279°. Its hue sits on the cool side of the wheel. The nearest named color is Dark Periwinkle (#665FD1), ΔE 0.038 away. White text reads best on it, at 4.76:1.
| Hue family | Blues |
| Lightness | medium-dark (56%) |
| Chroma | moderately saturated (0.134) |
| Temperature | cool |
| Nearest name | Dark Periwinkle (#665FD1) |
| Black text | 4.40:1 |
| White text | 4.76:1 |
Values
| HEX | #666AC2 |
| RGB | rgb(102, 106, 194) |
| HSL | hsl(237, 43%, 58%) |
| OKLCH | oklch(56.3% 0.134 279.2) |
Contrast
WCAG 2 contrast ratios are the conformance target: AA needs 4.5:1 for body text and 3:1 for large text, AAA needs 7:1. APCA Lc values are supplementary guidance from the WCAG 3 drafts.
| Pair | WCAG 2 | Result | APCA | APCA guidance |
|---|---|---|---|---|
| White text on #666AC2 | 4.76:1 | AA | Lc -78.4 | Fine for body text |
| Black text on #666AC2 | 4.40:1 | AA large text | Lc 31.1 | Non-text elements, placeholder text |
| #666AC2 text on white | 4.76:1 | AA | Lc 72.9 | Content text, not long reading |
| #666AC2 text on black | 4.40:1 | AA large text | Lc -28.8 | Dividers and decoration only |
Tints and shades
A 50–950 scale built in OKLCH: the hue is held, lightness follows a Tailwind v4-like curve, and every step is kept inside the sRGB gamut. This color sits at step 600.
-
Step 50
50
#F4F5FB
oklch(97.1% 0.008 278.6)
-
Step 100
100
#E7E9F6
oklch(93.6% 0.018 279.1)
-
Step 200
200
#D4D7F0
oklch(88.5% 0.034 280.2)
-
Step 300
300
#B8BDE8
oklch(80.9% 0.061 279.7)
-
Step 400
400
#949ADC
oklch(70.7% 0.097 279.6)
-
Step 500
500
#7A80D3
oklch(63.1% 0.124 279.1)
-
Step 600
600 (this color)
#666AC2
oklch(56.3% 0.134 279.2)
-
Step 700
700
#5356A5
oklch(49% 0.124 279.1)
-
Step 800
800
#444786
oklch(42.7% 0.103 279)
-
Step 900
900
#393C6B
oklch(37.7% 0.08 279.1)
-
Step 950
950
#21233F
oklch(26.9% 0.052 279.2)
#666AC2 with color blindness
Simulated with the Machado et al. (2009) model. ΔE is how far the color moves: below about 0.02 you would not notice a change.
| Vision | Seen as | Shift (ΔE) |
|---|---|---|
| Protanopia (no red cones) | #4676C5 | 0.046 |
| Deuteranopia (no green cones) | #3F6FC0 | 0.047 |
| Tritanopia (no blue cones) | #457D8C | 0.119 |
| Achromatopsia (no color) | #737373 | 0.134 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666AC2
#666AC2
oklch(56.3% 0.134 279.2)
- #867600
#867600
oklch(56.3% 0.117 99.8)
Analogous
Neighbouring hues, 30° either side.
Split complementary
The two hues beside the complement (150° and 210°).
Triadic
Three hues spaced 120° apart.
Palettes with this color
Curated palettes that contain a color within ΔE 0.04 (OKLab) of #666AC2, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dark Periwinkle #665FD1 ΔE 0.038
- Slate Blue #6A5ACD ΔE 0.045
- Light Indigo #6D5ACF ΔE 0.047
- Iris #6258C4 ΔE 0.047
- French Blue #436BAD ΔE 0.057
- Windows Blue #3778BF ΔE 0.060
- Royal Blue #4169E1 ΔE 0.065
- Deep Lavender #8D5EB7 ΔE 0.066
Use #666AC2 in your product
Turn it into light and dark UI roles checked for contrast, then export to Tailwind v4, shadcn/ui, CSS or design tokens.