#637CB3
Closest named color: Off Blue (#5684AE). oklch(59% 0.09 265.1), rgb(99, 124, 179).
Aa
Black text reads best on this color (5.06:1).
About this color
#637CB3 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 59%, its chroma 0.090 and its hue 265°. Its hue sits on the cool side of the wheel. The nearest named color is Off Blue (#5684AE), ΔE 0.029 away. Black text reads best on it, at 5.06:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | moderately saturated (0.090) |
| Temperature | cool |
| Nearest name | Off Blue (#5684AE) |
| Black text | 5.06:1 |
| White text | 4.14:1 |
Values
| HEX | #637CB3 |
| RGB | rgb(99, 124, 179) |
| HSL | hsl(221, 34%, 55%) |
| OKLCH | oklch(59% 0.09 265.1) |
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 #637CB3 | 4.14:1 | AA large text | Lc -74.0 | Content text, not long reading |
| Black text on #637CB3 | 5.06:1 | AA | Lc 35.6 | Non-text elements, placeholder text |
| #637CB3 text on white | 4.14:1 | AA large text | Lc 68.5 | Content text, not long reading |
| #637CB3 text on black | 5.06:1 | AA | Lc -33.2 | 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
#D2D9E8
oklch(88.4% 0.022 265.8)
-
Step 300
300
#B4C1DC
oklch(81% 0.041 265)
-
Step 400
400
#8DA0CA
oklch(70.6% 0.065 265.8)
-
Step 500
500
#7189BC
oklch(63.2% 0.082 264.7)
-
Step 600
600 (this color)
#637CB3
oklch(59% 0.09 265.1)
-
Step 700
700
#495F90
oklch(49% 0.084 265.1)
-
Step 800
800
#3C4E75
oklch(42.7% 0.069 264.7)
-
Step 900
900
#34415E
oklch(37.7% 0.053 265.4)
-
Step 950
950
#1E2637
oklch(26.9% 0.034 264.8)
#637CB3 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) | #6880B5 | 0.014 |
| Deuteranopia (no green cones) | #6079B2 | 0.010 |
| Tritanopia (no blue cones) | #468890 | 0.080 |
| Achromatopsia (no color) | #7C7C7C | 0.090 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637CB3
#637CB3
oklch(59% 0.09 265.1)
- #967939
#967939
oklch(59.1% 0.09 85)
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 #637CB3, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Off Blue #5684AE ΔE 0.029
- Cool Blue #4984B8 ΔE 0.033
- Dusty Blue #5A86AD ΔE 0.033
- Steel Blue #4682B4 ΔE 0.033
- Stormy Blue #507B9C ΔE 0.044
- Faded Blue #658CBB ΔE 0.044
- Cerulean #457B9D ΔE 0.051
- Windows Blue #3778BF ΔE 0.052
Use #637CB3 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.