Description
In 3.6 Matching media features and media types, current Use Case Requirement says:
However, displaying a color image on monochrome media (e.g., paper and e-ink displays) can be problematic: different colors with similar luminosity are impossible to distinguish on monochrome media. This problem is illustrated in the figure below, where it becomes nearly impossible to associate slices of a pie chart with corresponding labels.
(snip)
The only feasible solution is for authors to provide alternative image content that communicates effectively in monochrome media.
This is a common accessibility issue/mistake and fails WCAG 2.0 Success Criterion 1.4.1 Use of Color.
Yet there are some cases where authors cannot modify existing problematic contents, Use Case Requirements should mention this is an accessibility issue and authors are encouraged to avoid relying color alone.
Related resources: