#666BB0
Closest named color: French Blue (#436BAD). oklch(55.4% 0.107 279.2), rgb(102, 107, 176).
Aa
White text reads best on this color (4.88:1).
About this color
#666BB0 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 55%, its chroma 0.107 and its hue 279°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.045 away. White text reads best on it, at 4.88:1.
| Hue family | Blues |
| Lightness | medium-dark (55%) |
| Chroma | moderately saturated (0.107) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.29:1 |
| White text | 4.88:1 |
Values
| HEX | #666BB0 |
| RGB | rgb(102, 107, 176) |
| HSL | hsl(236, 32%, 55%) |
| OKLCH | oklch(55.4% 0.107 279.2) |
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 #666BB0 | 4.88:1 | AA | Lc -79.2 | Fine for body text |
| Black text on #666BB0 | 4.29:1 | AA large text | Lc 30.3 | Non-text elements, placeholder text |
| #666BB0 text on white | 4.88:1 | AA | Lc 73.8 | Content text, not long reading |
| #666BB0 text on black | 4.29:1 | AA large text | Lc -27.9 | 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
#E8E9F3
oklch(93.6% 0.013 281.6)
-
Step 200
200
#D5D8EB
oklch(88.6% 0.026 278.7)
-
Step 300
300
#B9BEE0
oklch(80.9% 0.048 278.7)
-
Step 400
400
#969CD0
oklch(70.7% 0.076 279.1)
-
Step 500
500
#7D83C4
oklch(63.1% 0.098 279.2)
-
Step 600
600 (this color)
#666BB0
oklch(55.4% 0.107 279.2)
-
Step 700
700
#555998
oklch(49% 0.1 279.3)
-
Step 800
800
#46497B
oklch(42.6% 0.082 279.7)
-
Step 900
900
#3A3E63
oklch(37.8% 0.063 278.2)
-
Step 950
950
#22243A
oklch(26.9% 0.041 279.3)
#666BB0 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) | #5374B3 | 0.032 |
| Deuteranopia (no green cones) | #4E6EAE | 0.032 |
| Tritanopia (no blue cones) | #4F7985 | 0.094 |
| Achromatopsia (no color) | #717171 | 0.107 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666BB0
#666BB0
oklch(55.4% 0.107 279.2)
- #827318
#827318
oklch(55.3% 0.106 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 #666BB0, closest first.
No curated palette has a color within ΔE 0.04 of #666BB0.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.045
- Flat Blue #3C73A8 ΔE 0.055
- Dark Lavender #856798 ΔE 0.059
- Windows Blue #3778BF ΔE 0.059
- Dull Blue #49759C ΔE 0.059
- Muted Blue #3B719F ΔE 0.062
- Iris #6258C4 ΔE 0.063
- Dark Periwinkle #665FD1 ΔE 0.064
Use #666BB0 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.