#637DB7
Closest named color: Off Blue (#5684AE). oklch(59.4% 0.094 265.2), rgb(99, 125, 183).
Aa
Black text reads best on this color (5.14:1).
About this color
#637DB7 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 59%, its chroma 0.094 and its hue 265°. Its hue sits on the cool side of the wheel. The nearest named color is Off Blue (#5684AE), ΔE 0.030 away. Black text reads best on it, at 5.14:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | moderately saturated (0.094) |
| Temperature | cool |
| Nearest name | Off Blue (#5684AE) |
| Black text | 5.14:1 |
| White text | 4.07:1 |
Values
| HEX | #637DB7 |
| RGB | rgb(99, 125, 183) |
| HSL | hsl(221, 37%, 55%) |
| OKLCH | oklch(59.4% 0.094 265.2) |
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 #637DB7 | 4.07:1 | AA large text | Lc -73.4 | Content text, not long reading |
| Black text on #637DB7 | 5.14:1 | AA | Lc 36.2 | Non-text elements, placeholder text |
| #637DB7 text on white | 4.07:1 | AA large text | Lc 67.9 | Content text, not long reading |
| #637DB7 text on black | 5.14:1 | AA | Lc -33.8 | 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 500.
-
Step 50
50
#F3F5FA
oklch(97% 0.007 268.5)
-
Step 100
100
#E5EAF3
oklch(93.6% 0.013 262.4)
-
Step 200
200
#D1D9EB
oklch(88.5% 0.026 266.6)
-
Step 300
300
#B2C1DF
oklch(80.9% 0.046 264.3)
-
Step 400
400
#8AA0CF
oklch(70.6% 0.074 265.1)
-
Step 500
500 (this color)
#637DB7
oklch(59.4% 0.094 265.2)
-
Step 600
600
#5671AF
oklch(55.5% 0.102 265.4)
-
Step 700
700
#465F97
oklch(49.2% 0.095 264.9)
-
Step 800
800
#3A4D7A
oklch(42.6% 0.079 265.8)
-
Step 900
900
#324162
oklch(37.8% 0.06 265)
-
Step 950
950
#1D263A
oklch(27% 0.04 265.3)
#637DB7 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) | #6882B9 | 0.016 |
| Deuteranopia (no green cones) | #5F7AB6 | 0.010 |
| Tritanopia (no blue cones) | #438992 | 0.084 |
| Achromatopsia (no color) | #7E7E7E | 0.094 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637DB7
#637DB7
oklch(59.4% 0.094 265.2)
- #987A35
#987A35
oklch(59.4% 0.095 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 #637DB7, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Off Blue #5684AE ΔE 0.030
- Cool Blue #4984B8 ΔE 0.032
- Steel Blue #4682B4 ΔE 0.034
- Dusty Blue #5A86AD ΔE 0.034
- Faded Blue #658CBB ΔE 0.042
- Stormy Blue #507B9C ΔE 0.049
- Windows Blue #3778BF ΔE 0.051
- Cerulean #457B9D ΔE 0.055
Use #637DB7 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.