#666DA8
Closest named color: French Blue (#436BAD). oklch(55.4% 0.092 277.8), rgb(102, 109, 168).
Aa
White text reads best on this color (4.86:1).
About this color
#666DA8 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 55%, its chroma 0.092 and its hue 278°. 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 4.86:1.
| Hue family | Blues |
| Lightness | medium-dark (55%) |
| Chroma | moderately saturated (0.092) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.31:1 |
| White text | 4.86:1 |
Values
| HEX | #666DA8 |
| RGB | rgb(102, 109, 168) |
| HSL | hsl(234, 27%, 53%) |
| OKLCH | oklch(55.4% 0.092 277.8) |
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 #666DA8 | 4.86:1 | AA | Lc -79.1 | Fine for body text |
| Black text on #666DA8 | 4.31:1 | AA large text | Lc 30.4 | Non-text elements, placeholder text |
| #666DA8 text on white | 4.86:1 | AA | Lc 73.7 | Content text, not long reading |
| #666DA8 text on black | 4.31:1 | AA large text | Lc -28.0 | 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
#F4F5F9
oklch(97.1% 0.005 275)
-
Step 100
100
#E8E9F2
oklch(93.6% 0.012 281.1)
-
Step 200
200
#D5D8E9
oklch(88.5% 0.023 277.9)
-
Step 300
300
#BABFDC
oklch(81% 0.041 277.7)
-
Step 400
400
#969DCA
oklch(70.7% 0.066 277.7)
-
Step 500
500
#7D85BC
oklch(63.2% 0.083 277.4)
-
Step 600
600 (this color)
#666DA8
oklch(55.4% 0.092 277.8)
-
Step 700
700
#555B91
oklch(49% 0.087 277.9)
-
Step 800
800
#464B75
oklch(42.7% 0.07 277.8)
-
Step 900
900
#3A3F5F
oklch(37.8% 0.055 276.6)
-
Step 950
950
#222537
oklch(27% 0.034 276.6)
#666DA8 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) | #5974AA | 0.024 |
| Deuteranopia (no green cones) | #556FA7 | 0.023 |
| Tritanopia (no blue cones) | #527983 | 0.081 |
| Achromatopsia (no color) | #717171 | 0.092 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666DA8
#666DA8
oklch(55.4% 0.092 277.8)
- #81732C
#81732C
oklch(55.4% 0.092 98.1)
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 #666DA8, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.045
- Dull Blue #49759C ΔE 0.048
- Flat Blue #3C73A8 ΔE 0.050
- Dark Lavender #856798 ΔE 0.052
- Stormy Blue #507B9C ΔE 0.054
- Muted Blue #3B719F ΔE 0.055
- Metallic Blue #4F738E ΔE 0.058
- Cerulean #457B9D ΔE 0.060
Use #666DA8 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.