All borders need a contrast ratio of at least 3.0:1 against their backgrounds. This includes borders on actionable elements like text inputs, radio buttons, and checkboxes.
Check the color contrast of your borders and learn more about best practices with these excellent color contrast tools:
- Color Contrast Analyzer (Chrome Extension)
- TPG’s Color Contrast Analyser
- tanaguru contrast finder
- WebAIM’s Contrast Checker