Never Use Color Alone to Convey Information
This sometimes sounds counterintuitive: making a warning red or a success alert green is second nature to most designers. While color can act as a shorthand for most users, those with color blindness can find themselves at a disadvantage. Certain types of color blindness will mean that users can’t tell the difference between a red status blob and a green one.
The best way to approach this is to use color to convey additional information, and not just use color alone. This makes the site usable for most people, but not at the expense of a few. Therefore I advise making links underlined (and, optionally, a different color), not just a different color, to differentiate them from body copy.
Another example is that a “status normal” label could show a green indicator blob, but should never just be the green blob on its own.
Figure 69.1: Only one of these interfaces is usable for color-blind people
