Technique G183:Using a contrast ratio of 3:1 with surrounding text and providing additional visual cues on hover for links or controls where color alone is used to identify them
About this Technique
This technique relates to 1.4.1: Use of Color (Sufficient).
This technique applies to colored text when color alone is used to convey information such as words that are links in a paragraph.
Description
The intent of this technique is to provide a redundant visual cue for users who may not be able to discern a difference in text color. Color (generally defined as a combination of hue, saturation and luminance) is commonly used to indicate words that are links within a paragraph or other block of text. For example, scattered words in text may be hypertext links that are identified only by a difference in color with surrounding text. This technique describes a way to provide a difference in contrast rather than relying on hue.
To meet success criterion 1.4.1: Use of Color a relative luminance (lightness) difference of 3:1 or greater with the text around can be used. This technique goes beyond the success criterion and asks for visual highlights when the user hovers over each link, such as an underline, a change in font style such as bold or italics, or an increase in font size. Such a hover effect provides confirmation to pointer users that the text is a link, similar to how the link alters its appearance for keyboard users when it receives focus, in order to meet 2.4.7 Focus Visible.
While using this technique is sufficient to meet this success criterion, it is not the preferred technique to differentiate link text. This is because links that use the relative luminance of color alone may not be obvious to people with low vision. If there are not a large number of links in the block of text, underlines are recommended for links in blocks of text.
Note
This technique is about the use of color in addition to luminosity. In this technique, the contrast ratio refers to the contrast between a link and the words around it. In Success Criterion 1.4.3 and 1.4.6, contrast ratio refers to the contrast between a word and its background. The difference is that this technique is about the ability for users to tell the difference (a noticeable difference) between different pieces of text whereas the contrast ratio used in success criterion 1.4.3 and 1.4.6 is about the readability of the text with its background for different color and vision disabilities.
If an author wants to use the color portion of this technique (i.e., using different colors for the words where the colors have sufficient contrast with each other) and the author also wants to conform to SC 1.4.3 (contrast of both words with their backgrounds) the following colors can be used. (e.g., black text in a paragraph on a white background with the links shown as one of the colors in example 1 below.
If assistive technology or Web browsers at some point all provide an option to underline all links on Web pages for users, this could be used instead of an author-provided link highlighting mechanism.
Examples
Example 1: Colors that would provide 3:1 contrast with black words and 4.5:1 contrast with a white background
Refer to Links with a 3:1 contrast ratio with surrounding text
Example 2
The hypertext links in a document are medium-light blue (#3366CC) and the regular text is black (#000000). Beyond the difference in color, the links have no other styles differences compared with the regular text. Because the blue text is light enough, it has a contrast of 3.9:1 with the surrounding text and can be identified as being different from the surrounding text by people with all types of color blindness, including those individuals who cannot see color at all. In addition to the contrast difference, the links have :focus and :hover styles that reintroduce the underline when the links receive keyboard focus or when a mouse pointer hovers over them. Hover or focus style changes alone are not sufficient to meet the criterion.
Related Resources
No endorsement implied.
Tests
Procedure
For each instance where color is used to convey information about text:
- Check that the relative luminance of the color of the text differs from the relative luminance of the surrounding text by a contrast ratio of at least 3:1.
- Check that hovering over the link causes a visual enhancement (such as an underline, font change, etc.)
Expected Results
- Checks #1 and #2 are true.