Suficient contrast

• Normal text (14px and more) should have a contrast ratio of at least 4.5:1
• Large text (at least 24px regular or 18px bold) should have a contrast ratio of at least 3:1
• Try to avoid text smaller than 14px since it might be very difficult to read

There is a growing list of tools that help you to find the right colors:

• WebAim Contrast Checker is probably the most known one
• Contrast Grid helps you to check your full color palette and to identify color combinations you should avoid.
• Stark is a very powerful multi platform assistant that supports you during the design process.
• The axe DevTools browser extension scans your application and identifies color contrast issues in your current UI (and much more).

There are exceptions:

• Inactive or disabled interface components
• Purely decorative elements
• Logos