How do you know which colors will have enough contrast to be universally readable? One approach, of course, is to play it safe and stick to black and white, which are the default colors in applications like Microsoft Word. But color is an important—some would say essential—design element of slide presentations and the Web. So, which colors are best?
When text is placed against a solid color background, we recommend you use the Colour Contrast Analyser (CCA) by the Paciello Group to determine whether the contrast ratio passes the WCAG 2.0 standards. This free tool helps you “determine the legibility of text and the contrast of visual elements” using color contrast criteria established in the Web Content Accessibility Guidelines (WCAG) 2.0. The tool also simulates certain visual conditions, including dichromatic color-blindness and cataracts, to demonstrate how your web content appears to people with less than 20/20 vision. Use the CCA eyedropper tool to select foreground and background colors. The results display immediately below.
In the following example, we’ve run the CCA on a website designed with orange headings, gray text, and blue link text.
For this website, the CCA reports insufficient contrast between orange text and the white background. You would want to select a darker orange color from the drop-down color palette.
When we check the gray text against white background, the CCA shows mixed results. This color combination passes at the "AA" standard, but not the more stringent "AAA" standard, which is the goal for most university and public websites. A darker gray would be better.
Finally, we test the blue link text against the white background. This combination of colors fails both the “AA” and “AAA” standards for normal text sizes, as well as the “AAA” test for larger sizes. It passes only the “AA” standard for large text. A darker blue is required for universal readability.