#3F66C9
Closest named color: Royal Blue (#4169E1). oklch(53.5% 0.16 265.2), rgb(63, 102, 201).
Aa
White text reads best on this color (5.30:1).
About this color
#3F66C9 is a medium-dark, vivid blue. In OKLCH its lightness is 54%, its chroma 0.160 and its hue 265°. Its hue sits on the cool side of the wheel. The nearest named color is Royal Blue (#4169E1), ΔE 0.037 away. White text reads best on it, at 5.30:1.
| Hue family | Blues |
| Lightness | medium-dark (54%) |
| Chroma | vivid (0.160) |
| Temperature | cool |
| Nearest name | Royal Blue (#4169E1) |
| Black text | 3.95:1 |
| White text | 5.30:1 |
Values
| HEX | #3F66C9 |
| RGB | rgb(63, 102, 201) |
| HSL | hsl(223, 56%, 52%) |
| OKLCH | oklch(53.5% 0.16 265.2) |
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 #3F66C9 | 5.30:1 | AA | Lc -81.4 | Fine for body text |
| Black text on #3F66C9 | 3.95:1 | AA large text | Lc 28.0 | Dividers and decoration only |
| #3F66C9 text on white | 5.30:1 | AA | Lc 76.1 | Fine for body text |
| #3F66C9 text on black | 3.95:1 | AA large text | Lc -25.7 | 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
#F2F5FC
oklch(97% 0.01 267.4)
-
Step 100
100
#E3EAF8
oklch(93.6% 0.02 264.5)
-
Step 200
200
#CCD9F4
oklch(88.4% 0.04 265.1)
-
Step 300
300
#AAC0F0
oklch(80.8% 0.072 265.6)
-
Step 400
400
#7E9FE9
oklch(70.8% 0.115 265.3)
-
Step 500
500
#5D85E2
oklch(63.1% 0.147 265)
-
Step 600
600 (this color)
#3F66C9
oklch(53.5% 0.16 265.2)
-
Step 700
700
#365AB4
oklch(49.1% 0.149 265)
-
Step 800
800
#2D4A92
oklch(42.7% 0.124 265.1)
-
Step 900
900
#283E74
oklch(37.6% 0.096 265.4)
-
Step 950
950
#182544
oklch(27% 0.061 265.4)
#3F66C9 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) | #2E72CD | 0.032 |
| Deuteranopia (no green cones) | #0065C7 | 0.036 |
| Tritanopia (no blue cones) | #007D8E | 0.130 |
| Achromatopsia (no color) | #6B6B6B | 0.160 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #3F66C9
#3F66C9
oklch(53.5% 0.16 265.2)
- #8A6700
#8A6700
oklch(53.5% 0.11 85.1)
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 #3F66C9, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Royal Blue #4169E1 ΔE 0.037
- Mid Blue #276AB3 ΔE 0.043
- Warm Blue #4B57DB ΔE 0.048
- French Blue #436BAD ΔE 0.048
- Iris #6258C4 ΔE 0.052
- Dark Periwinkle #665FD1 ΔE 0.052
- Windows Blue #3778BF ΔE 0.053
- Neon Blue #4361EE ΔE 0.059
Use #3F66C9 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.