#666AAC
Closest named color: French Blue (#436BAD). oklch(55% 0.102 279.8), rgb(102, 106, 172).
Aa
White text reads best on this color (4.97:1).
About this color
#666AAC is a medium-dark, moderately saturated blue. In OKLCH its lightness is 55%, its chroma 0.102 and its hue 280°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.044 away. White text reads best on it, at 4.97:1.
| Hue family | Blues |
| Lightness | medium-dark (55%) |
| Chroma | moderately saturated (0.102) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.22:1 |
| White text | 4.97:1 |
Values
| HEX | #666AAC |
| RGB | rgb(102, 106, 172) |
| HSL | hsl(237, 30%, 54%) |
| OKLCH | oklch(55% 0.102 279.8) |
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 #666AAC | 4.97:1 | AA | Lc -79.7 | Fine for body text |
| Black text on #666AAC | 4.22:1 | AA large text | Lc 29.7 | Dividers and decoration only |
| #666AAC text on white | 4.97:1 | AA | Lc 74.3 | Content text, not long reading |
| #666AAC text on black | 4.22:1 | AA large text | Lc -27.4 | 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
#D5D8EA
oklch(88.5% 0.025 278.3)
-
Step 300
300
#BABEDF
oklch(80.9% 0.047 279.8)
-
Step 400
400
#979CCE
oklch(70.7% 0.073 279.9)
-
Step 500
500
#7E83C2
oklch(63.1% 0.095 279.8)
-
Step 600
600 (this color)
#666AAC
oklch(55% 0.102 279.8)
-
Step 700
700
#565A95
oklch(49.1% 0.094 279.4)
-
Step 800
800
#474A79
oklch(42.8% 0.077 279.8)
-
Step 900
900
#3B3E62
oklch(37.8% 0.061 279.4)
-
Step 950
950
#232439
oklch(27% 0.039 281.4)
#666AAC 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) | #5372AF | 0.030 |
| Deuteranopia (no green cones) | #4F6DAA | 0.031 |
| Tritanopia (no blue cones) | #517783 | 0.089 |
| Achromatopsia (no color) | #707070 | 0.102 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666AAC
#666AAC
oklch(55% 0.102 279.8)
- #80721E
#80721E
oklch(54.9% 0.102 99.4)
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 #666AAC, closest first.
No curated palette has a color within ΔE 0.04 of #666AAC.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.044
- Flat Blue #3C73A8 ΔE 0.054
- Dark Lavender #856798 ΔE 0.056
- Dull Blue #49759C ΔE 0.057
- Muted Blue #3B719F ΔE 0.059
- Windows Blue #3778BF ΔE 0.062
- Stormy Blue #507B9C ΔE 0.065
- Iris #6258C4 ΔE 0.065
Use #666AAC 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.