#666CB9
Closest named color: French Blue (#436BAD). oklch(56.1% 0.118 278.5), rgb(102, 108, 185).
Aa
White text reads best on this color (4.76:1).
About this color
#666CB9 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 56%, its chroma 0.118 and its hue 278°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.049 away. White text reads best on it, at 4.76:1.
| Hue family | Blues |
| Lightness | medium-dark (56%) |
| Chroma | moderately saturated (0.118) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.41:1 |
| White text | 4.76:1 |
Values
| HEX | #666CB9 |
| RGB | rgb(102, 108, 185) |
| HSL | hsl(236, 37%, 56%) |
| OKLCH | oklch(56.1% 0.118 278.5) |
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 #666CB9 | 4.76:1 | AA | Lc -78.4 | Fine for body text |
| Black text on #666CB9 | 4.41:1 | AA large text | Lc 31.1 | Non-text elements, placeholder text |
| #666CB9 text on white | 4.76:1 | AA | Lc 72.9 | Content text, not long reading |
| #666CB9 text on black | 4.41:1 | 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
#F4F5FA
oklch(97.1% 0.007 277.2)
-
Step 100
100
#E7E9F4
oklch(93.6% 0.015 277.8)
-
Step 200
200
#D4D8ED
oklch(88.6% 0.029 277.2)
-
Step 300
300
#B8BEE3
oklch(80.9% 0.053 277.9)
-
Step 400
400
#949BD6
oklch(70.6% 0.087 278.7)
-
Step 500
500
#7B82CA
oklch(63.1% 0.108 278.6)
-
Step 600
600 (this color)
#666CB9
oklch(56.1% 0.118 278.5)
-
Step 700
700
#53589E
oklch(49% 0.111 278.4)
-
Step 800
800
#444980
oklch(42.8% 0.091 277.9)
-
Step 900
900
#393D67
oklch(37.7% 0.072 278.2)
-
Step 950
950
#21243C
oklch(27% 0.045 277.5)
#666CB9 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) | #4F76BC | 0.036 |
| Deuteranopia (no green cones) | #4970B7 | 0.037 |
| Tritanopia (no blue cones) | #4A7C89 | 0.105 |
| Achromatopsia (no color) | #737373 | 0.119 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666CB9
#666CB9
oklch(56.1% 0.118 278.5)
- #877500
#877500
oklch(56.2% 0.116 98.5)
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 #666CB9, closest first.
No curated palette has a color within ΔE 0.04 of #666CB9.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.049
- Dark Periwinkle #665FD1 ΔE 0.053
- Windows Blue #3778BF ΔE 0.056
- Iris #6258C4 ΔE 0.057
- Slate Blue #6A5ACD ΔE 0.058
- Light Indigo #6D5ACF ΔE 0.060
- Flat Blue #3C73A8 ΔE 0.061
- Deep Lavender #8D5EB7 ΔE 0.067
Use #666CB9 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.