#666ACB
Closest named color: Dark Periwinkle (#665FD1). oklch(56.8% 0.147 278.8), rgb(102, 106, 203).
Aa
White text reads best on this color (4.67:1).
About this color
#666ACB is a medium-dark, vivid blue. In OKLCH its lightness is 57%, its chroma 0.147 and its hue 279°. Its hue sits on the cool side of the wheel. The nearest named color is Dark Periwinkle (#665FD1), ΔE 0.030 away. White text reads best on it, at 4.67:1.
| Hue family | Blues |
| Lightness | medium-dark (57%) |
| Chroma | vivid (0.147) |
| Temperature | cool |
| Nearest name | Dark Periwinkle (#665FD1) |
| Black text | 4.48:1 |
| White text | 4.67:1 |
Values
| HEX | #666ACB |
| RGB | rgb(102, 106, 203) |
| HSL | hsl(238, 49%, 60%) |
| OKLCH | oklch(56.8% 0.147 278.8) |
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 #666ACB | 4.67:1 | AA | Lc -77.7 | Fine for body text |
| Black text on #666ACB | 4.48:1 | AA large text | Lc 31.8 | Non-text elements, placeholder text |
| #666ACB text on white | 4.67:1 | AA | Lc 72.3 | Content text, not long reading |
| #666ACB text on black | 4.48:1 | AA large text | Lc -29.4 | 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
#F4F5FC
oklch(97.1% 0.009 279.7)
-
Step 100
100
#E7E9F7
oklch(93.7% 0.019 279.5)
-
Step 200
200
#D3D7F2
oklch(88.4% 0.037 278.9)
-
Step 300
300
#B7BDEC
oklch(81% 0.067 279.1)
-
Step 400
400
#9299E2
oklch(70.6% 0.107 279.1)
-
Step 500
500
#797FD9
oklch(63.2% 0.134 278.9)
-
Step 600
600 (this color)
#666ACB
oklch(56.8% 0.147 278.8)
-
Step 700
700
#5254AC
oklch(49% 0.137 279.1)
-
Step 800
800
#43468B
oklch(42.8% 0.112 278.7)
-
Step 900
900
#383B6F
oklch(37.7% 0.088 278.8)
-
Step 950
950
#212341
oklch(27% 0.055 279.1)
#666ACB 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) | #3F78CF | 0.052 |
| Deuteranopia (no green cones) | #3670C9 | 0.054 |
| Tritanopia (no blue cones) | #3F7F91 | 0.128 |
| Achromatopsia (no color) | #747474 | 0.147 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666ACB
#666ACB
oklch(56.8% 0.147 278.8)
- #897700
#897700
oklch(56.9% 0.118 98.6)
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 #666ACB, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dark Periwinkle #665FD1 ΔE 0.030
- Slate Blue #6A5ACD ΔE 0.039
- Light Indigo #6D5ACF ΔE 0.040
- Iris #6258C4 ΔE 0.046
- Royal Blue #4169E1 ΔE 0.055
- Medium Slate Blue #7B68EE ΔE 0.062
- Windows Blue #3778BF ΔE 0.065
- French Blue #436BAD ΔE 0.066
Use #666ACB 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.