Color and Contrast

Accessibility Techniques for Color contrast and use of color
Topic Technique WCAG AA Requirement
Use of Color Use of Color: Any information conveyed by color MUST be accompanied by a programmatically discernible text alternative.
Testing methodology 1.4.1.a
Required
WCAG 1.4.1
Visible Alternative: Any information conveyed by color MUST be accompanied by a visible alternative (text, image, etc.) that does not depend on color for meaning.
Testing methodology 1.4.1.a
Required
WCAG 1.4.1
Color Contrast

Small Text Contrast: Small text (under 18 point regular font or 14 point bold font) MUST have a contrast ratio of at least 4.5 to 1 with the background.

Note: The contrast rule also applies to images of text, even though images of text are discouraged.

Testing methodology 1.4.3.a
Required
WCAG 1.4.3

Large Text Contrast: Large text (at or over 18 point or 14 point bold) MUST have a contrast ratio of at least 3 to 1 with the background.

Note: The contrast rule also applies to images of text, even though images of text are discouraged.

Testing methodology 1.4.3.b
Required
WCAG 1.4.3
UI Component Contrast: The contrast of UI control boundaries compared to adjacent areas MUST be at least 3 to 1 to distinguish the UI control from the adjacent areas.
Testing methodology 1.4.11.a
Testing methodology 1.4.11.c
Required
WCAG 1.4.11 (WCAG 2.1)
Visual Focus Indicator Contrast: The contrast of all visual focus indicators against the background MUST be at least 3 to 1.
Testing methodology 1.4.11.b
Required
WCAG 1.4.11 (WCAG 2.1)
High Contrast Mode Retain Visible Information: Web content SHOULD retain all essential visual information in Windows High Contrast Mode. Best Practice
Don't Override: The design SHOULD NOT override Windows High Contrast Mode. Best Practice