#637BB1
Closest named color: Off Blue (#5684AE). oklch(58.7% 0.088 265.4), rgb(99, 123, 177).
Aa
Black text reads best on this color (4.99:1).
About this color
#637BB1 is a medium-dark, moderately saturated blue. In OKLCH its lightness is 59%, its chroma 0.088 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 4.99:1.
| Hue family | Blues |
| Lightness | medium-dark (59%) |
| Chroma | moderately saturated (0.088) |
| Temperature | cool |
| Nearest name | Off Blue (#5684AE) |
| Black text | 4.99:1 |
| White text | 4.20:1 |
Values
| HEX | #637BB1 |
| RGB | rgb(99, 123, 177) |
| HSL | hsl(222, 33%, 54%) |
| OKLCH | oklch(58.7% 0.088 265.4) |
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 #637BB1 | 4.20:1 | AA large text | Lc -74.4 | Content text, not long reading |
| Black text on #637BB1 | 4.99:1 | AA | Lc 35.2 | Non-text elements, placeholder text |
| #637BB1 text on white | 4.20:1 | AA large text | Lc 68.9 | Content text, not long reading |
| #637BB1 text on black | 4.99:1 | AA | Lc -32.8 | 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 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
#B4C1DB
oklch(80.9% 0.039 264.3)
-
Step 400
400
#8EA0C9
oklch(70.6% 0.064 266.3)
-
Step 500
500
#7289BB
oklch(63.2% 0.08 265.1)
-
Step 600
600 (this color)
#637BB1
oklch(58.7% 0.088 265.4)
-
Step 700
700
#4A5F8F
oklch(49% 0.082 265.5)
-
Step 800
800
#3D4E74
oklch(42.7% 0.067 265.3)
-
Step 900
900
#34415E
oklch(37.7% 0.053 265.4)
-
Step 950
950
#1F2637
oklch(27% 0.033 266.9)
#637BB1 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) | #687FB3 | 0.014 |
| Deuteranopia (no green cones) | #6078B0 | 0.010 |
| Tritanopia (no blue cones) | #47868E | 0.079 |
| Achromatopsia (no color) | #7C7C7C | 0.088 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637BB1
#637BB1
oklch(58.7% 0.088 265.4)
- #94783A
#94783A
oklch(58.6% 0.088 85.1)
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 #637BB1, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Off Blue #5684AE ΔE 0.030
- Steel Blue #4682B4 ΔE 0.034
- Cool Blue #4984B8 ΔE 0.034
- Dusty Blue #5A86AD ΔE 0.034
- Stormy Blue #507B9C ΔE 0.042
- Faded Blue #658CBB ΔE 0.047
- Cerulean #457B9D ΔE 0.049
- Dull Blue #49759C ΔE 0.049
Use #637BB1 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.