Some users have difficulty perceiving color. People with partial sight often experience limited color vision, and many older users do not see color well. In addition, people using text-only, limited-color or monochrome displays and browsers will be unable to access information that is presented only in color. In order to avoid this, check that any information conveyed by color is also available in text. For example, ensure that charts do not use only color as a key, and that links are distinguishable by something other than their color (for example, via an underline).