Do not rely solely on color to convey meaning or distinguish elements. For example, indicating links only by turning the text blue makes them indistinguishable for readers using monochrome displays or those with color vision deficiencies.
Objectives
Ensure information is accessible to users who cannot distinguish colors due to their device settings, reading software, or visual impairments (such as color blindness)
Improve content accessibility for people with disabilities
Implementation
Supplement color with a secondary indicator to convey the information. This complementary, independent of the CSS formatting layer, can be multiple orders, e.g. :
Prevent semantic markup (strong, em, etc. ;
Add axes, patterns, borders, etc. in maps and charts.
Control
Verification requires visually comparing two types of display of book : normal display and color display will be disabled (rendered to computer screen and rendered to smooth with greyscale screen).
Verification requires visually comparing two types of display of book : normal display and color display will be disabled (rendered to computer screen and rendered to smooth with greyscale screen).