n Open Author, you can use the Accessibility Checker to instantly identify and solve any accessibility issues in your content. The Accessibility Checker identifies and reports instances where content lacks proper color contrast, font size, alternative text for images, etc. Solving these accessibility issues will ensure that everyone can access your new content, including those who use screen readers and screen magnifiers.

This is the Check Accessibility button on the toolbar in the Main Content field of Open Author:

Select the Check Accessibility button to have the Accessibilty Checker review your content and display any accessibility issues one at a time. You can then decide whether to ignore an issue (leave as is) or to solve an issue. You can use the Quick fix feature to automatically solve each issue, or you can manually fix each issue.

More in-depth information on how to use the Accessibility Checker 

Example of an accessibilty issue: