#666EB3
Closest named color: French Blue (#436BAD). oklch(56.2% 0.107 277.4), rgb(102, 110, 179).
Aa
White text reads best on this color (4.72:1).
About this color
#666EB3 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 56%, its chroma 0.107 and its hue 277°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.047 away. White text reads best on it, at 4.72:1.
| Hue family | Blues |
| Lightness | medium-dark (56%) |
| Chroma | moderately saturated (0.107) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.44:1 |
| White text | 4.72:1 |
Values
| HEX | #666EB3 |
| RGB | rgb(102, 110, 179) |
| HSL | hsl(234, 34%, 55%) |
| OKLCH | oklch(56.2% 0.107 277.4) |
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 #666EB3 | 4.72:1 | AA | Lc -78.2 | Fine for body text |
| Black text on #666EB3 | 4.44:1 | AA large text | Lc 31.4 | Non-text elements, placeholder text |
| #666EB3 text on white | 4.72:1 | AA | Lc 72.7 | Content text, not long reading |
| #666EB3 text on black | 4.44:1 | AA large text | Lc -29.0 | 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
#E7E9F3
oklch(93.5% 0.014 277.1)
-
Step 200
200
#D4D8EB
oklch(88.5% 0.026 276.4)
-
Step 300
300
#B8BEE0
oklch(80.8% 0.048 277.4)
-
Step 400
400
#949CD1
oklch(70.6% 0.078 277.6)
-
Step 500
500
#7B83C5
oklch(63% 0.1 277.8)
-
Step 600
600 (this color)
#666EB3
oklch(56.2% 0.107 277.4)
-
Step 700
700
#535A98
oklch(49.1% 0.099 277.2)
-
Step 800
800
#444A7B
oklch(42.7% 0.081 277.1)
-
Step 900
900
#393E63
oklch(37.7% 0.064 277)
-
Step 950
950
#21243A
oklch(26.8% 0.041 277.3)
#666EB3 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) | #5676B6 | 0.027 |
| Deuteranopia (no green cones) | #5070B1 | 0.029 |
| Tritanopia (no blue cones) | #4D7C88 | 0.094 |
| Achromatopsia (no color) | #737373 | 0.107 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666EB3
#666EB3
oklch(56.2% 0.107 277.4)
- #87751A
#87751A
oklch(56.3% 0.107 97.2)
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 #666EB3, closest first.
No curated palette has a color within ΔE 0.04 of #666EB3.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.047
- Flat Blue #3C73A8 ΔE 0.054
- Windows Blue #3778BF ΔE 0.055
- Dull Blue #49759C ΔE 0.058
- Dark Lavender #856798 ΔE 0.061
- Steel Blue #4682B4 ΔE 0.062
- Muted Blue #3B719F ΔE 0.063
- Stormy Blue #507B9C ΔE 0.064
Use #666EB3 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.