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
d e ficient 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.
Sources: Bailey, 1996; Chisholm, Vanderheiden and Jacobs, 1999c; Evans, 1998; Hess, 2000; Levine, 1996; Murch, 1985; Rigden, 1999; Smith and Mosier, 1986; Sullivan and Matson, 2000; Thorell and Smith, 1990; Tullis , 2001; United States Government, 1998; Wolfmaier, 1999; Vischeck, 2003.
