#666FBA
Closest named color: French Blue (#436BAD). oklch(56.8% 0.116 276.9), rgb(102, 111, 186).
Aa
White text reads best on this color (4.61:1).
About this color
#666FBA is a medium-dark, moderately saturated blue. In OKLCH its lightness is 57%, its chroma 0.116 and its hue 277°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.051 away. White text reads best on it, at 4.61:1.
| Hue family | Blues |
| Lightness | medium-dark (57%) |
| Chroma | moderately saturated (0.116) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 4.54:1 |
| White text | 4.61:1 |
Values
| HEX | #666FBA |
| RGB | rgb(102, 111, 186) |
| HSL | hsl(234, 38%, 56%) |
| OKLCH | oklch(56.8% 0.116 276.9) |
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 #666FBA | 4.61:1 | AA | Lc -77.4 | Fine for body text |
| Black text on #666FBA | 4.54:1 | AA | Lc 32.1 | Non-text elements, placeholder text |
| #666FBA text on white | 4.61:1 | AA | Lc 72.0 | Content text, not long reading |
| #666FBA text on black | 4.54:1 | AA | Lc -29.7 | 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
#D4D8ED
oklch(88.6% 0.029 277.2)
-
Step 300
300
#B7BEE3
oklch(80.8% 0.053 276.7)
-
Step 400
400
#939CD5
oklch(70.7% 0.084 277.1)
-
Step 500
500
#7983C9
oklch(63.1% 0.106 276.7)
-
Step 600
600 (this color)
#666FBA
oklch(56.8% 0.116 276.9)
-
Step 700
700
#52599D
oklch(49.1% 0.108 277.2)
-
Step 800
800
#43497F
oklch(42.6% 0.089 277.1)
-
Step 900
900
#383E66
oklch(37.8% 0.069 276.1)
-
Step 950
950
#21243C
oklch(27% 0.045 277.5)
#666FBA 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) | #5378BD | 0.031 |
| Deuteranopia (no green cones) | #4D72B8 | 0.032 |
| Tritanopia (no blue cones) | #497E8B | 0.102 |
| Achromatopsia (no color) | #757575 | 0.116 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #666FBA
#666FBA
oklch(56.8% 0.116 276.9)
- #8A7605
#8A7605
oklch(56.8% 0.116 97.1)
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 #666FBA, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.051
- Windows Blue #3778BF ΔE 0.053
- Dark Periwinkle #665FD1 ΔE 0.058
- Flat Blue #3C73A8 ΔE 0.059
- Steel Blue #4682B4 ΔE 0.063
- Cool Blue #4984B8 ΔE 0.064
- Slate Blue #6A5ACD ΔE 0.064
- Iris #6258C4 ΔE 0.064
Use #666FBA 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.