1.4.11 Non-text contrast (Level AA)
Having high contrast between pieces of text and their backgrounds is one of the best and most important things you can do to ensure great accessibility on your website.

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In this guideline the requirement for high contrast extends from regular page text, to text on interface components (buttons) as well as for colors used in non-text content (infographics and diagrams).

Specifies the minimum contrast (3:1) for graphical elements and user interface components (for example indicators, buttons). Of course, not all graphical objects needs contrast, only those required for the user to understand what graphic is conveying (for example print icon).

Example:

1.4.11 Non-text contrast (Level AA)