Use color sparingly
When using color or sensory-based instructions (for example, size, shape, position, etc) in a document, providing supplemental information for users with visual impairments is necessary. To ensure accessibility, you should also be mindful when choosing a document's colors.
Sharp contrast between the text and background colors in a document help people read the content more easily, regardless of visual impairments or the content medium. Low color contrast can make text difficult to read. Try to use simple, high-contrast color combinations such as black on a white background, or white on a black background.
For example: "The assignments in red contained in the box on the left side of the page are due next week." would be difficult to understand for individuals with visual impairments, since they might not be able to tell which assignments were marked red.
However, "Look in the Weekly Due Date section under the Assignments heading. The assignments in red and marked with an asterisk (*) are due next week." provides the same information but the color-, shape-, and size-dependent instructions are supplemented by searchable text indicators like an asterisk and "Assignments" text.
There are a number of websites available that can help test for color contrast issues in a document. One example is Contrast Finder, a site that helps find contrast issues in documents. As an alternative to web-based tools, you can print a sample of the document in black and white or grayscale, and then look for any contrast issues that appear.