#637FBB
Closest named color: Cool Blue (#4984B8). oklch(60% 0.098 264.5), rgb(99, 127, 187).
Aa
Black text reads best on this color (5.28:1).
About this color
#637FBB is a medium-dark, moderately saturated blue. In OKLCH its lightness is 60%, its chroma 0.098 and its hue 265°. Its hue sits on the cool side of the wheel. The nearest named color is Cool Blue (#4984B8), ΔE 0.031 away. Black text reads best on it, at 5.28:1.
| Hue family | Blues |
| Lightness | medium-dark (60%) |
| Chroma | moderately saturated (0.098) |
| Temperature | cool |
| Nearest name | Cool Blue (#4984B8) |
| Black text | 5.28:1 |
| White text | 3.97:1 |
Values
| HEX | #637FBB |
| RGB | rgb(99, 127, 187) |
| HSL | hsl(221, 39%, 56%) |
| OKLCH | oklch(60% 0.098 264.5) |
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 #637FBB | 3.97:1 | AA large text | Lc -72.5 | Content text, not long reading |
| Black text on #637FBB | 5.28:1 | AA | Lc 37.1 | Non-text elements, placeholder text |
| #637FBB text on white | 3.97:1 | AA large text | Lc 67.0 | Content text, not long reading |
| #637FBB text on black | 5.28:1 | AA | Lc -34.7 | 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
#D0D9EB
oklch(88.4% 0.027 264.4)
-
Step 300
300
#B1C1E0
oklch(80.9% 0.047 263.7)
-
Step 400
400
#89A0D1
oklch(70.6% 0.077 265)
-
Step 500
500 (this color)
#637FBB
oklch(60% 0.098 264.5)
-
Step 600
600
#5471B2
oklch(55.6% 0.107 264.9)
-
Step 700
700
#445F99
oklch(49.2% 0.099 264.2)
-
Step 800
800
#384D7C
oklch(42.6% 0.083 264.9)
-
Step 900
900
#314164
oklch(37.8% 0.064 264.8)
-
Step 950
950
#1D263A
oklch(27% 0.04 265.3)
#637FBB 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) | #6984BE | 0.017 |
| Deuteranopia (no green cones) | #5F7CBA | 0.010 |
| Tritanopia (no blue cones) | #408C95 | 0.087 |
| Achromatopsia (no color) | #808080 | 0.098 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637FBB
#637FBB
oklch(60% 0.098 264.5)
- #9B7B34
#9B7B34
oklch(60% 0.097 84.6)
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 #637FBB, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Cool Blue #4984B8 ΔE 0.031
- Off Blue #5684AE ΔE 0.031
- Steel Blue #4682B4 ΔE 0.035
- Dusty Blue #5A86AD ΔE 0.035
- Faded Blue #658CBB ΔE 0.037
- Windows Blue #3778BF ΔE 0.052
- Stormy Blue #507B9C ΔE 0.055
- Cerulean #457B9D ΔE 0.060
Use #637FBB 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.