Ensure that all information conveyed with color is also available without color.

Never use color as the only indicator for critical activities. About eight percent of males and about one-half of one percent of females have difficulty discriminating colors. Most users with color deficiencies have difficulty seeing colors in the green portion of the spectrum.

To accommodate color-deficient users, designers should:

• Select color combinations that can be discriminated by users with color deficiencies;
• Use tools to see what Web pages will look like when seen by color deficient users;
• Ensure that the lightness contrast between foreground and background colors is high;
• Increase the lightness contrast between colors on either end of the spectrum (e.g., blues and reds); and
• Avoid combining light colors from either end of the spectrum with dark colors from the middle of the spectrum.