Overview
Color should not be used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.
Ensure that all sighted users can access information that is conveyed by color differences, that is, by the use of color where each color has a meaning assigned to it. If the information is conveyed through color differences in an image (or other non-text format), the color may not be seen by users with color deficiencies. In this case, providing the information conveyed with color through another visual means ensures users who cannot see color can still perceive the information.
Color is an important asset in the design of Web content, enhancing its aesthetic appeal, its usability, and its accessibility. However, some users have difficulty perceiving color. People with partial sight often experience limited color vision, and many older users do not see color well. In addition, people using limited-color or monochrome displays and browsers will be unable to access information that is presented only in color.
Provide sufficient contrast:
Between text and its background, so that it can be read by people with moderately low vision or impaired contrast perception, without the use of contrast-enhancing assistive technology.
Between link text and background color.
Between link text and surrounding body text.
Color Contrast Between Text and Background Color
Provide sufficient color contrast between foreground and background, text and background color.
The contrast ratio between text and background, using regular body text, should be at least 4.5:1.
Large-scale text (24 pixels or 18 pixels bolded) should have a contrast ratio of at least 3:1.
Test your contrast level using this color contrast checker for WCAG AA compliance https://webaim.org/resources/contrastchecker/
Color Contrast Between a) Link Text and Background Color and b) Link Text and Surrounding Body Text
There should be a contrast ratio of at least 4.5.1 between link text and background color. This applies to regular body text (or 3:1 for large text) .
There must be a 3.1 contrast ratio between link text and surrounding text.
Use this link contrast checker to test color contrasts for links https://webaim.org/resources/linkcontrastchecker/
Color Blindness
When designing for color blindness, make sure that colors are not your only method of conveying important information.
Use this filter to test web pages for color blindness https://www.toptal.com/designers/colorfilter/
If the purpose of posting the content is to communicate something about the colors in that image or web page, then it is important to provide some other way of understanding the information.
Challenges | Solutions |
Reds and greens are often indistinguishable | This is not normally a problem except in cases where the colors convey important information. Under these circumstances you will need to either change the content or graphic or provide an additional means of obtaining the same information. For example, provide an explanation in the text itself. |
Color and Messaging
Don’t rely on color to convey critical information such as alerts and error messages. See more info about this under the Alert/Error Messaging section.