#637A91
Closest named color: Grey Blue (#647D8E). oklch(57% 0.045 248.6), rgb(99, 122, 145).
Aa
Black text reads best on this color (4.72:1).
About this color
#637A91 is a medium-dark, muted blue. In OKLCH its lightness is 57%, its chroma 0.045 and its hue 249°. Its hue sits on the cool side of the wheel. The nearest named color is Grey Blue (#647D8E), ΔE 0.011 away. Black text reads best on it, at 4.72:1.
| Hue family | Blues |
| Lightness | medium-dark (57%) |
| Chroma | muted (0.045) |
| Temperature | cool |
| Nearest name | Grey Blue (#647D8E) |
| Black text | 4.72:1 |
| White text | 4.44:1 |
Values
| HEX | #637A91 |
| RGB | rgb(99, 122, 145) |
| HSL | hsl(210, 19%, 48%) |
| OKLCH | oklch(57% 0.045 248.6) |
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 #637A91 | 4.44:1 | AA large text | Lc -76.3 | Fine for body text |
| Black text on #637A91 | 4.72:1 | AA | Lc 33.2 | Non-text elements, placeholder text |
| #637A91 text on white | 4.44:1 | AA large text | Lc 70.8 | Content text, not long reading |
| #637A91 text on black | 4.72:1 | AA | Lc -30.8 | 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
#F4F6F7
oklch(97.2% 0.003 228.8)
-
Step 100
100
#E7EAEE
oklch(93.6% 0.006 255.5)
-
Step 200
200
#D4DAE0
oklch(88.6% 0.011 247.9)
-
Step 300
300
#B7C2CD
oklch(80.9% 0.02 248.1)
-
Step 400
400
#92A3B4
oklch(70.8% 0.031 248.3)
-
Step 500
500
#768CA2
oklch(63.1% 0.042 248.5)
-
Step 600
600 (this color)
#637A91
oklch(57% 0.045 248.6)
-
Step 700
700
#4E6378
oklch(49.1% 0.042 248.7)
-
Step 800
800
#405161
oklch(42.7% 0.034 247.1)
-
Step 900
900
#37434F
oklch(37.7% 0.026 248.5)
-
Step 950
950
#20272F
oklch(26.9% 0.018 251.9)
#637A91 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) | #717A92 | 0.019 |
| Deuteranopia (no green cones) | #6C7591 | 0.018 |
| Tritanopia (no blue cones) | #557F81 | 0.038 |
| Achromatopsia (no color) | #787878 | 0.045 |
Harmonies
Hue rotations in OKLCH that keep this color's lightness and chroma.
Complementary
The opposite hue (180°).
- #637A91
#637A91
oklch(57% 0.045 248.6)
- #89735B
#89735B
oklch(57% 0.045 69.2)
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 #637A91, closest first.
Similar named colors
The eight closest entries in our named color list, with their ΔE distance.
- Grey Blue #647D8E ΔE 0.011
- Battleship Grey #6B7C85 ΔE 0.023
- Stormy Blue #507B9C ΔE 0.026
- Slate Gray #708090 ΔE 0.027
- Battleship Gray #6C757D ΔE 0.031
- Steel Grey #6F828A ΔE 0.034
- Metallic Blue #4F738E ΔE 0.034
- Cerulean #457B9D ΔE 0.037
Use #637A91 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.