color and contrast
Guidelines
WCAG 2.0
1.3.2 When information is conveyed by color, the color can be programmatically determined or the information is also conveyed through another means that does not depend on the user's ability to differentiate colors.
1.4.3 Text or diagrams, and their background, must have a luminosity contrast ratio of at least 10:1.
section 508
§508.1194.22(c) Web pages shall be designed so that all information conveyed with color is also available without color, for example from context or markup.
Goals
- Information conveyed only in color is not available to people who do not perceive color
- Whenever color conveys information, make sure that other parts of the page convey the same information
- This applies to link color also. Provide some formatting, in addition to color, to differentiate links from text.
- Be sure that there is adequate contrast between text and background
- Text or diagrams, and their background, must have a sufficient luminosity contrast ratio to distinguish foreground from background.
- Luminosity ratio of 10:1 is the best.