#637FBC
Closest named color: Cool Blue (#4984B8). oklch(60.1% 0.099 264.8), rgb(99, 127, 188).
Aa
Black text reads best on this color (5.29:1).
About this color
#637FBC is a medium-dark, moderately saturated blue. In OKLCH its lightness is 60%, its chroma 0.099 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 5.29:1.
| Hue family | Blues |
| Lightness | medium-dark (60%) |
| Chroma | moderately saturated (0.099) |
| Temperature | cool |
| Nearest name | Cool Blue (#4984B8) |
| Black text | 5.29:1 |
| White text | 3.96:1 |
Values
| HEX | #637FBC |
| RGB | rgb(99, 127, 188) |
| HSL | hsl(221, 40%, 56%) |
| OKLCH | oklch(60.1% 0.099 264.8) |
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 #637FBC | 3.96:1 | AA large text | Lc -72.4 | Content text, not long reading |
| Black text on #637FBC | 5.29:1 | AA | Lc 37.1 | Non-text elements, placeholder text |
| #637FBC text on white | 3.96:1 | AA large text | Lc 66.9 | Content text, not long reading |
| #637FBC text on black | 5.29:1 | 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
#E5EAF4
oklch(93.6% 0.015 264.5)
-
Step 200
200
#D0D9EC
oklch(88.4% 0.028 265.4)
-
Step 300
300
#B1C1E1
oklch(80.9% 0.049 264.3)
-
Step 400
400
#89A0D2
oklch(70.7% 0.078 265.3)
-
Step 500
500 (this color)
#637FBC
oklch(60.1% 0.099 264.8)
-
Step 600
600
#5471B2
oklch(55.6% 0.107 264.9)
-
Step 700
700
#445E99
oklch(49% 0.1 265)
-
Step 800
800
#384D7C
oklch(42.6% 0.083 264.9)
-
Step 900
900
#304164
oklch(37.8% 0.064 263.8)
-
Step 950
950
#1C263B
oklch(27% 0.042 264.3)
#637FBC 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) | #6884BF | 0.016 |
| Deuteranopia (no green cones) | #5F7CBB | 0.010 |
| Tritanopia (no blue cones) | #3F8C95 | 0.089 |
| Achromatopsia (no color) | #808080 | 0.099 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637FBC
#637FBC
oklch(60.1% 0.099 264.8)
- #9C7B32
#9C7B32
oklch(60% 0.099 84.4)
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 #637FBC, 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 0.033
- Steel Blue #4682B4 ΔE 0.035
- Dusty Blue #5A86AD ΔE 0.036
- Faded Blue #658CBB ΔE 0.038
- Windows Blue #3778BF ΔE 0.052
- Stormy Blue #507B9C ΔE 0.056
- Water Blue #0E87CC ΔE 0.061
Use #637FBC 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.