#3F66A4
Closest named color: French Blue (#436BAD). oklch(51.1% 0.108 259.3), rgb(63, 102, 164).
Aa
White text reads best on this color (5.75:1).
About this color
#3F66A4 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 51%, its chroma 0.108 and its hue 259°. Its hue sits on the cool side of the wheel. The nearest named color is French Blue (#436BAD), ΔE 0.019 away. White text reads best on it, at 5.75:1.
| Hue family | Blues |
| Lightness | medium-dark (51%) |
| Chroma | moderately saturated (0.108) |
| Temperature | cool |
| Nearest name | French Blue (#436BAD) |
| Black text | 3.64:1 |
| White text | 5.75:1 |
Values
| HEX | #3F66A4 |
| RGB | rgb(63, 102, 164) |
| HSL | hsl(217, 44%, 45%) |
| OKLCH | oklch(51.1% 0.108 259.3) |
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 #3F66A4 | 5.75:1 | AA | Lc -83.9 | Fine for body text |
| Black text on #3F66A4 | 3.64:1 | AA large text | Lc 25.5 | Dividers and decoration only |
| #3F66A4 text on white | 5.75:1 | AA | Lc 78.6 | Fine for body text |
| #3F66A4 text on black | 3.64:1 | AA large text | Lc -23.2 | 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 700.
-
Step 50
50
#F3F6FA
oklch(97.2% 0.006 255.5)
-
Step 100
100
#E4EAF4
oklch(93.5% 0.015 260.7)
-
Step 200
200
#CEDAED
oklch(88.5% 0.029 259.6)
-
Step 300
300
#ADC2E3
oklch(80.9% 0.052 259.4)
-
Step 400
400
#81A2D5
oklch(70.7% 0.084 258.9)
-
Step 500
500
#618ACA
oklch(63.1% 0.107 259)
-
Step 600
600
#4873B7
oklch(55.6% 0.117 259.2)
-
Step 700
700 (this color)
#3F66A4
oklch(51.1% 0.108 259.3)
-
Step 800
800
#304F80
oklch(42.8% 0.09 259.2)
-
Step 900
900
#2A4267
oklch(37.8% 0.07 258.8)
-
Step 950
950
#19273C
oklch(27.1% 0.044 258.3)
#3F66A4 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) | #4C6BA7 | 0.022 |
| Deuteranopia (no green cones) | #3E62A3 | 0.012 |
| Tritanopia (no blue cones) | #00747D | 0.092 |
| Achromatopsia (no color) | #666666 | 0.108 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #3F66A4
#3F66A4
oklch(51.1% 0.108 259.3)
- #865E00
#865E00
oklch(51.1% 0.106 79.7)
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 #3F66A4, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- French Blue #436BAD ΔE 0.019
- Dusky Blue #475F94 ΔE 0.029
- Mid Blue #276AB3 ΔE 0.029
- Muted Blue #3B719F ΔE 0.035
- Flat Blue #3C73A8 ΔE 0.036
- Denim #3B638C ΔE 0.039
- Denim Blue #3B5B92 ΔE 0.040
- Peacock Blue #016795 ΔE 0.047
Use #3F66A4 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.