Colors are an important issue for users who do not perceive colors at all, especially people who are blind, who have very low vision, or who have color vision deficiencies (color blindness for example).
Sometimes, the color is used as the only way to convey information. For example, in a list, you have set the required elements in red and left the optional elements in black. A user who can not see these colors will not have access to this information. You must always provide another means, and preferably textual, so that all users, regardless of their ability to perceive, can access this information.
Another issue related to color concerns contrasts. For a user who has difficulty perceiving contrasts, some text may be impossible to read if its color is not sufficiently contrasted with the background color.
- Do not give information only by color;
- Readability of the contents.