Understanding Color Contrast Ratio Requirements on the University of Maine System website
What Are Color Contrast Ratios?
Color contrast ratio usually means the ratio between the color of text (or additional important visual information) and the color of the background, which must meet minimum ratio levels to ensure legibility for visually-impaired and/or color blind users.
You can use this tool to test your contrast ratio (External Site).
Color Contrast Ratios Guidance
Using color photographs or graphics in University of Maine System web pages is acceptable as a way to create visual interest and break up a text-heavy page, as long as the image is only decorative in nature. The overwhelming majority of site visitors will experience color in a consistent, predictable way. A number of these visitors (about 4.5%) will have some kind of color insensitivity or “color blindness.” Consideration must be given toward how the use of color could impact their experience.
Whenever using color in images, ensure that the colors have a contrast ratio of at least 4.5:1. This ensures that the text is still readable to those who may have color blindness. There are online tools to check color contrast ratio such as this one provided by WebAIM (External Site).
Color should not convey meaning by itself
Because color blindness affects how some visitors experience color, you should not rely on it to convey meaning without additional visual cues. If there is no indication aside from a color, you will not get the attention of a colorblind person.
Accessible color contrast also ratios help low-vision users
Color contrast ratios are often discussed from the perspective that this accessibility requirement primarily helps users who experience colorblindness. But color contrast ratios are important for many users. Users who have developed visual disabilities as they have aged, users who experience temporary visual impairments from surgeries or temporary medical conditions, and users who wear glasses or do not have 20/20 vision may all benefit from proper color contrast ratios.