#337ACB
Closest named color: Windows Blue (#3778BF). oklch(57.5% 0.144 254), rgb(51, 122, 203).
Aa
Black text reads best on this color (4.78:1).
About this color
#337ACB is a medium-dark, vivid blue. In OKLCH its lightness is 58%, its chroma 0.144 and its hue 254°. Its hue sits on the cool side of the wheel. The nearest named color is Windows Blue (#3778BF), ΔE 0.018 away. Black text reads best on it, at 4.78:1.
| Hue family | Blues |
| Lightness | medium-dark (58%) |
| Chroma | vivid (0.144) |
| Temperature | cool |
| Nearest name | Windows Blue (#3778BF) |
| Black text | 4.78:1 |
| White text | 4.38:1 |
Values
| HEX | #337ACB |
| RGB | rgb(51, 122, 203) |
| HSL | hsl(212, 60%, 50%) |
| OKLCH | oklch(57.5% 0.144 254) |
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 #337ACB | 4.38:1 | AA large text | Lc -75.5 | Fine for body text |
| Black text on #337ACB | 4.78:1 | AA | Lc 34.0 | Non-text elements, placeholder text |
| #337ACB text on white | 4.38:1 | AA large text | Lc 70.0 | Content text, not long reading |
| #337ACB text on black | 4.78:1 | AA | Lc -31.6 | Non-text elements, placeholder text |
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
#F2F6FB
oklch(97.2% 0.008 253.9)
-
Step 100
100
#E2EBF6
oklch(93.7% 0.018 253.3)
-
Step 200
200
#C9DBF1
oklch(88.5% 0.036 253.5)
-
Step 300
300
#A4C3EA
oklch(80.8% 0.065 254.3)
-
Step 400
400
#72A4E0
oklch(70.7% 0.103 253.6)
-
Step 500
500
#4C8CD7
oklch(63.2% 0.131 253.8)
-
Step 600
600 (this color)
#337ACB
oklch(57.5% 0.144 254)
-
Step 700
700
#1F61AA
oklch(49.1% 0.134 254.1)
-
Step 800
800
#1C4F8A
oklch(42.6% 0.112 254.5)
-
Step 900
900
#1D426E
oklch(37.6% 0.087 254.4)
-
Step 950
950
#122740
oklch(26.9% 0.054 254)
#337ACB 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) | #5380CE | 0.036 |
| Deuteranopia (no green cones) | #3B72C9 | 0.021 |
| Tritanopia (no blue cones) | #008D98 | 0.110 |
| Achromatopsia (no color) | #787878 | 0.144 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #337ACB
#337ACB
oklch(57.5% 0.144 254)
- #A36C00
#A36C00
oklch(57.5% 0.122 74)
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 #337ACB, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Windows Blue #3778BF ΔE 0.018
- Water Blue #0E87CC ΔE 0.036
- Nice Blue #107AB0 ΔE 0.048
- Steel Blue #4682B4 ΔE 0.049
- Cool Blue #4984B8 ΔE 0.049
- Flat Blue #3C73A8 ΔE 0.054
- French Blue #436BAD ΔE 0.056
- Mid Blue #276AB3 ΔE 0.056
Use #337ACB 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.