#666BB4
Closest named color: French Blue (#436BAD). oklch(55.7% 0.113 279.1), rgb(102, 107, 180).
Aa
White text reads best on this color (4.85:1).
About this color
#666BB4 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 56%, its chroma 0.113 and its hue 279°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.046 away. White text reads best on it, at 4.85:1.
| Hue family | Blues |
| Lightness | medium-dark (56%) |
| Chroma | moderately saturated (0.113) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.32:1 |
| White text | 4.85:1 |
Values
| HEX | #666BB4 |
| RGB | rgb(102, 107, 180) |
| HSL | hsl(236, 34%, 55%) |
| OKLCH | oklch(55.7% 0.113 279.1) |
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 #666BB4 | 4.85:1 | AA | Lc -79.0 | Fine for body text |
| Black text on #666BB4 | 4.32:1 | AA large text | Lc 30.5 | Non-text elements, placeholder text |
| #666BB4 text on white | 4.85:1 | AA | Lc 73.6 | Content text, not long reading |
| #666BB4 text on black | 4.32:1 | AA large text | Lc -28.1 | 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
#D5D8EC
oklch(88.6% 0.028 279)
-
Step 300
300
#B9BEE2
oklch(80.9% 0.051 279)
-
Step 400
400
#959CD3
oklch(70.8% 0.081 278.5)
-
Step 500
500
#7C82C7
oklch(63% 0.104 279.2)
-
Step 600
600 (this color)
#666BB4
oklch(55.7% 0.113 279.1)
-
Step 700
700
#55599B
oklch(49.2% 0.105 279.2)
-
Step 800
800
#45497D
oklch(42.7% 0.086 278.8)
-
Step 900
900
#3A3D65
oklch(37.6% 0.068 279.3)
-
Step 950
950
#22243B
oklch(27% 0.043 279.3)
#666BB4 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) | #5174B7 | 0.033 |
| Deuteranopia (no green cones) | #4B6FB2 | 0.035 |
| Tritanopia (no blue cones) | #4D7A87 | 0.099 |
| Achromatopsia (no color) | #717171 | 0.113 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666BB4
#666BB4
oklch(55.7% 0.113 279.1)
- #84740A
#84740A
oklch(55.7% 0.113 99.3)
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 #666BB4, closest first.
No curated palette has a color within ΔE 0.04 of #666BB4.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.046
- Flat Blue #3C73A8 ΔE 0.058
- Windows Blue #3778BF ΔE 0.058
- Dark Periwinkle #665FD1 ΔE 0.058
- Iris #6258C4 ΔE 0.059
- Slate Blue #6A5ACD ΔE 0.062
- Dark Lavender #856798 ΔE 0.062
- Dull Blue #49759C ΔE 0.063
Use #666BB4 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.