ColorWell · contrast check
White or black text on #64748b?
Tailwind slate-500
Use white text. It gives 4.76:1, which passes AA, not AAA.
White text
4.76:1
passes AA, not AAA
Black text
4.41:1
passes AA for large text only (18pt+/14pt bold)
What the thresholds mean
| Level | Needs | White text | Black text |
|---|---|---|---|
| AA, normal text | 4.5:1 | pass | fail |
| AA, large text (18pt+/14pt bold) | 3:1 | pass | pass |
| AAA, normal text | 7:1 | fail | fail |
If you need the other one to pass
Same hue, moved along the lightness ramp until the ratio clears AA.
- For black text, use
#e9f3ff— 18.73:1
The colour itself
- Hex:
#64748b - RGB:
100, 116, 139 - Oklch:
55.44% 0.041 257
Shade ramp
#e9f3ff #d3dff1 #b7c5da #96a6bd #70819a #566479 #3d4859 #252e3c #101620
Paste this into your config
// tailwind.config.js
colors: {
brand: {
100: "#e9f3ff",
200: "#d3dff1",
300: "#b7c5da",
400: "#96a6bd",
500: "#70819a",
600: "#566479",
700: "#3d4859",
800: "#252e3c",
900: "#101620",
},
}Text colour to pair with the 500 shade (#70819a): black, at 5.3:1. For #64748b itself it is white, at 4.76:1.
Your own colours, the same way
Paste any hex and get this page for it live — ratio, verdict, ramp. Export the whole palette to CSS variables, a Tailwind config or Figma tokens when you want it in the project rather than on the screen.
Open ColorWellOther colours
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- text on #84cc16 Tailwind lime-500
- text on #22c55e Tailwind green-500
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- text on #14b8a6 Tailwind teal-500
- text on #06b6d4 Tailwind cyan-500
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- text on #3b82f6 Tailwind blue-500
- text on #6366f1 Tailwind indigo-500