#637BB3
Closest named color: Off Blue (#5684AE). oklch(58.8% 0.091 265.9), rgb(99, 123, 179).
Aa
Black text reads best on this color (5.01:1).
About this color
#637BB3 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 59%, its chroma 0.091 and its hue 266°. Its hue sits on the cool side of the wheel. The nearest named color is Off Blue (#5684AE), ΔE 0.031 away. Black text reads best on it, at 5.01:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | moderately saturated (0.091) |
| Temperature | cool |
| Nearest name | Off Blue (#5684AE) |
| Black text | 5.01:1 |
| White text | 4.18:1 |
Values
| HEX | #637BB3 |
| RGB | rgb(99, 123, 179) |
| HSL | hsl(222, 34%, 55%) |
| OKLCH | oklch(58.8% 0.091 265.9) |
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 #637BB3 | 4.18:1 | AA large text | Lc -74.3 | Content text, not long reading |
| Black text on #637BB3 | 5.01:1 | AA | Lc 35.3 | Non-text elements, placeholder text |
| #637BB3 text on white | 4.18:1 | AA large text | Lc 68.8 | Content text, not long reading |
| #637BB3 text on black | 5.01:1 | AA | Lc -32.9 | 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
#F4F5F9
oklch(97.1% 0.005 275)
-
Step 100
100
#E6EAF2
oklch(93.6% 0.012 264.5)
-
Step 200
200
#D2D9E9
oklch(88.5% 0.023 266.9)
-
Step 300
300
#B4C1DC
oklch(81% 0.041 265)
-
Step 400
400
#8DA0CA
oklch(70.6% 0.065 265.8)
-
Step 500
500
#7288BD
oklch(63.1% 0.084 266.7)
-
Step 600
600 (this color)
#637BB3
oklch(58.8% 0.091 265.9)
-
Step 700
700
#4A5F91
oklch(49.1% 0.085 266)
-
Step 800
800
#3D4E76
oklch(42.8% 0.07 266)
-
Step 900
900
#34415F
oklch(37.8% 0.054 265.9)
-
Step 950
950
#1E2638
oklch(27% 0.036 265.6)
#637BB3 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) | #6780B5 | 0.015 |
| Deuteranopia (no green cones) | #5F79B2 | 0.008 |
| Tritanopia (no blue cones) | #46878F | 0.082 |
| Achromatopsia (no color) | #7C7C7C | 0.091 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637BB3
#637BB3
oklch(58.8% 0.091 265.9)
- #957837
#957837
oklch(58.7% 0.091 85.2)
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 #637BB3, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Off Blue #5684AE ΔE 0.031
- Cool Blue #4984B8 ΔE 0.034
- Steel Blue #4682B4 ΔE 0.034
- Dusty Blue #5A86AD ΔE 0.036
- Stormy Blue #507B9C ΔE 0.045
- Faded Blue #658CBB ΔE 0.047
- Windows Blue #3778BF ΔE 0.051
- Cerulean #457B9D ΔE 0.051
Use #637BB3 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.