#3F66D1
Closest named color: Royal Blue (#4169E1). oklch(54.1% 0.171 265.8), rgb(63, 102, 209).
Aa
White text reads best on this color (5.20:1).
About this color
#3F66D1 is a medium-dark, vivid blue. In OKLCH its lightness is 54%, its chroma 0.171 and its hue 266°. Its hue sits on the cool side of the wheel. The nearest named color is Royal Blue (#4169E1), ΔE 0.025 away. White text reads best on it, at 5.20:1.
| Hue family | Blues |
| Lightness | medium-dark (54%) |
| Chroma | vivid (0.171) |
| Temperature | cool |
| Nearest name | Royal Blue (#4169E1) |
| Black text | 4.03:1 |
| White text | 5.20:1 |
Values
| HEX | #3F66D1 |
| RGB | rgb(63, 102, 209) |
| HSL | hsl(224, 61%, 53%) |
| OKLCH | oklch(54.1% 0.171 265.8) |
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 #3F66D1 | 5.20:1 | AA | Lc -80.8 | Fine for body text |
| Black text on #3F66D1 | 4.03:1 | AA large text | Lc 28.6 | Dividers and decoration only |
| #3F66D1 text on white | 5.20:1 | AA | Lc 75.4 | Fine for body text |
| #3F66D1 text on black | 4.03:1 | AA large text | Lc -26.3 | 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
#F2F5FD
oklch(97% 0.011 269.6)
-
Step 100
100
#E3EAF9
oklch(93.6% 0.022 265.8)
-
Step 200
200
#CCD9F6
oklch(88.5% 0.042 266.3)
-
Step 300
300
#A9C0F3
oklch(80.8% 0.077 265.8)
-
Step 400
400
#7C9EEE
oklch(70.7% 0.124 265.8)
-
Step 500
500
#5C84E8
oklch(63.2% 0.157 265.7)
-
Step 600
600 (this color)
#3F66D1
oklch(54.1% 0.171 265.8)
-
Step 700
700
#3558BA
oklch(49.1% 0.16 265.9)
-
Step 800
800
#2C4996
oklch(42.8% 0.131 265.6)
-
Step 900
900
#273E78
oklch(37.8% 0.103 265.5)
-
Step 950
950
#172546
oklch(27.1% 0.064 265.1)
#3F66D1 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) | #2374D5 | 0.038 |
| Deuteranopia (no green cones) | #0066CF | 0.035 |
| Tritanopia (no blue cones) | #007F92 | 0.137 |
| Achromatopsia (no color) | #6D6D6D | 0.171 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #3F66D1
#3F66D1
oklch(54.1% 0.171 265.8)
- #8C6900
#8C6900
oklch(54.1% 0.111 85.5)
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 #3F66D1, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Royal Blue #4169E1 ΔE 0.025
- Warm Blue #4B57DB ΔE 0.040
- Neon Blue #4361EE ΔE 0.047
- Dark Periwinkle #665FD1 ΔE 0.049
- Cerulean Blue #056EEE ΔE 0.052
- Iris #6258C4 ΔE 0.054
- Mid Blue #276AB3 ΔE 0.054
- Azul #1D5DEC ΔE 0.055
Use #3F66D1 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.