#666AE0
Closest named color: Dark Periwinkle (#665FD1). oklch(58.2% 0.176 278), rgb(102, 106, 224).
Aa
Black text reads best on this color (4.70:1).
About this color
#666AE0 is a medium-dark, vivid blue. In OKLCH its lightness is 58%, its chroma 0.176 and its hue 278°. Its hue sits on the cool side of the wheel. The nearest named color is Dark Periwinkle (#665FD1), ΔE 0.033 away. Black text reads best on it, at 4.70:1.
| Hue family | Blues |
| Lightness | medium-dark (58%) |
| Chroma | vivid (0.176) |
| Temperature | cool |
| Nearest name | Dark Periwinkle (#665FD1) |
| Black text | 4.70:1 |
| White text | 4.46:1 |
Values
| HEX | #666AE0 |
| RGB | rgb(102, 106, 224) |
| HSL | hsl(238, 66%, 64%) |
| OKLCH | oklch(58.2% 0.176 278) |
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 #666AE0 | 4.46:1 | AA large text | Lc -76.2 | Fine for body text |
| Black text on #666AE0 | 4.70:1 | AA | Lc 33.4 | Non-text elements, placeholder text |
| #666AE0 text on white | 4.46:1 | AA large text | Lc 70.7 | Content text, not long reading |
| #666AE0 text on black | 4.70:1 | AA | Lc -31.0 | Non-text elements, placeholder text |
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
#F3F5FD
oklch(97.1% 0.011 274.9)
-
Step 100
100
#E6E9FA
oklch(93.7% 0.023 277.9)
-
Step 200
200
#D2D7F7
oklch(88.5% 0.044 278.4)
-
Step 300
300
#B4BCF4
oklch(80.9% 0.08 278.1)
-
Step 400
400
#8E98EE
oklch(70.7% 0.126 277.6)
-
Step 500
500
#757BE9
oklch(63% 0.163 278.3)
-
Step 600
600 (this color)
#666AE0
oklch(58.2% 0.176 278)
-
Step 700
700
#4F50BA
oklch(49.1% 0.163 278.1)
-
Step 800
800
#404297
oklch(42.6% 0.136 277.9)
-
Step 900
900
#363978
oklch(37.7% 0.105 278)
-
Step 950
950
#1F2246
oklch(27% 0.066 277.4)
#666AE0 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) | #267CE4 | 0.068 |
| Deuteranopia (no green cones) | #0A72DE | 0.073 |
| Tritanopia (no blue cones) | #29859B | 0.154 |
| Achromatopsia (no color) | #777777 | 0.176 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666AE0
#666AE0
oklch(58.2% 0.176 278)
- #8E7B00
#8E7B00
oklch(58.3% 0.121 98.4)
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 #666AE0, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Dark Periwinkle #665FD1 ΔE 0.033
- Medium Slate Blue #7B68EE ΔE 0.037
- Light Indigo #6D5ACF ΔE 0.044
- Royal Blue #4169E1 ΔE 0.045
- Slate Blue #6A5ACD ΔE 0.045
- Cornflower #6A79F7 ΔE 0.049
- Neon Blue #4361EE ΔE 0.056
- Iris #6258C4 ΔE 0.059
Use #666AE0 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.