#637BB7
Closest named color: Off Blue (#5684AE). oklch(59% 0.097 266.8), rgb(99, 123, 183).
Aa
Black text reads best on this color (5.04:1).
About this color
#637BB7 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 59%, its chroma 0.097 and its hue 267°. Its hue sits on the cool side of the wheel. The nearest named color is Off Blue (#5684AE), ΔE 0.035 away. Black text reads best on it, at 5.04:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | moderately saturated (0.097) |
| Temperature | cool |
| Nearest name | Off Blue (#5684AE) |
| Black text | 5.04:1 |
| White text | 4.16:1 |
Values
| HEX | #637BB7 |
| RGB | rgb(99, 123, 183) |
| HSL | hsl(223, 37%, 55%) |
| OKLCH | oklch(59% 0.097 266.8) |
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 #637BB7 | 4.16:1 | AA large text | Lc -74.1 | Content text, not long reading |
| Black text on #637BB7 | 5.04:1 | AA | Lc 35.5 | Non-text elements, placeholder text |
| #637BB7 text on white | 4.16:1 | AA large text | Lc 68.6 | Content text, not long reading |
| #637BB7 text on black | 5.04:1 | AA | Lc -33.1 | 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
#E6EAF3
oklch(93.7% 0.013 266.7)
-
Step 200
200
#D2D9EA
oklch(88.5% 0.025 267.9)
-
Step 300
300
#B4C0DE
oklch(80.8% 0.044 268.1)
-
Step 400
400
#8DA0CD
oklch(70.7% 0.07 266.8)
-
Step 500
500
#7188C0
oklch(63.1% 0.089 266.8)
-
Step 600
600 (this color)
#637BB7
oklch(59% 0.097 266.8)
-
Step 700
700
#495E94
oklch(49% 0.091 266.9)
-
Step 800
800
#3C4D78
oklch(42.6% 0.075 266.8)
-
Step 900
900
#344061
oklch(37.6% 0.059 268.2)
-
Step 950
950
#1E2639
oklch(27% 0.037 266.4)
#637BB7 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) | #6580BA | 0.014 |
| Deuteranopia (no green cones) | #5D79B6 | 0.010 |
| Tritanopia (no blue cones) | #438891 | 0.087 |
| Achromatopsia (no color) | #7C7C7C | 0.097 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637BB7
#637BB7
oklch(59% 0.097 266.8)
- #967931
#967931
oklch(59% 0.097 86.9)
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 #637BB7, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Off Blue #5684AE ΔE 0.035
- Cool Blue #4984B8 ΔE 0.035
- Steel Blue #4682B4 ΔE 0.036
- Dusty Blue #5A86AD ΔE 0.039
- Faded Blue #658CBB ΔE 0.047
- Windows Blue #3778BF ΔE 0.049
- Stormy Blue #507B9C ΔE 0.050
- Dull Blue #49759C ΔE 0.056
Use #637BB7 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.