Color alone should not convey meaning

Avoid using color-only instructions, or using color alone to convey a certain message. For example, certain types of color blindness might make it difficult or even impossible to see important messages in a red font. Try to include An approach is to use both colors and symbols where people’s attention is required. 

Example

Often, color is used to indicate that something is very important.  This is a wise use of color, however, individuals who are color blind or have other visual disabilities will not be able to know that the color red below is used to draw attention and importance.  By adding an asterisks to the bulleted items in red font, there are now two ways for students to identify what information requires particular attention.  Color is therefore not the sole means of conveying importance. This is not to say, never use color in your document, but where you are able to edit color be sure there are multiple ways to determine meaning or information.

Use sufficient color contrast for font and symbols

If you must use color in your document, make sure the color contrast between the foreground (i.e. text or content) and the background color are sufficient. WCAG 2.0 Level AA standards require a luminosity of greater than 4.5:1 for normal text sizes. Some color combinations can be more difficult to read, be selective and conscious of the colors you choose.

Examples of Poor and Good Color Contrast

Resources

• WebAIM Color Contrast Checker
• Accessible color palette generator