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3:3 Do Not Use Color Alone to Convey Information

Relative Importance:

Relative Importance rating of 5 out of 5

Strength of Evidence:

Strength of Evidence rating of 4 out of 5

Document Type: Guideline


Topic:

Accessibility


Guideline:

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


Comments:

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.


Sources:

  • Bailey, R.W. (1996). Human performance engineering: Designing high quality professional user interfaces for computer products, applications and systems (3rd ed.). Englewood Cliffs, NJ: Prentice-Hall.
  • Chisholm, W., Vanderheiden, G., & Jacobs, I., Eds. (1999c). Web Content Accessibility Guidelines 1.0. Retrieved November 2005, from http://www.w3.org/TR/WCAG10/, Checkpoint 2.1.
  • Evans, M. (1998). Web Design: An Empiricist’s Guide. Unpublished master’s thesis. Seattle: University of Washington. Retrieved May 2003, from http://response.restoration.noaa.gov/webmastr/webdesgn.pdf.
  • Hess, R. (2000, October). Can color-blind users see your site? Microsoft Corporation. Retrieved November 2005, from http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnhess/html/hess10092000.asp.
  • Levine, R. (1996). Guide to Web Style. Sun Microsystems.
  • Murch, G.M. (1985, June). Colour graphics: Blessing or ballyhoo? Computer Graphics Forum, 4(2), 127-135.
  • Rigden, C. (1999). Safe Web colours for colour-deficient vision. British Telecommunications Engineering Journal; also retrieved November 2005 from http://www.btplc.com/age_disability/ClearerInformation/Colours/othersites.htm.
  • Smith, S.L. & Mosier, J.N. (1986, August). Guidelines for designing user interface software. The MITRE Corporation Technical Report (ESD-TR-86-278).
  • Sullivan, T. & Matson, R. (2000, November). Barriers to use: Usability and content accessibility on the Web’s most popular sites. Proceedings of the Conference on Universal Usability, 139-144. Retrieved November 2005, from http://www.pantos.org/ts/papers/BarriersToUse.pdf.
  • Thorell, L.G. & Smith, W.J. (1990). Using computer color effectively: An illustrated reference. Englewood Cliffs, NJ: Prentice Hall.
  • Tullis, T.S. (2001). Web usability lessons learned. Fidelity Center for Applied Technology Technical Report. Fidelity Investments.
  • United States Government, Rehabilitation Act of 1973 (amended in 1998), Section 508. Retrieved November 2005, from http://www.section508.gov/
  • Vischeck. Accessed November 2005, from http://www.vischeck.com/.
  • Wolfmaier, T.G. (1999). Designing for the color-challenged: A challenge. Internetworking. Retrieved November 2005, from http://www.internettg.org/newsletter/mar99/accessibility_color_challenged.html.

Related Resources:

  • Title: Section 508
    Description: Section 508 requires that Federal agencies' electronic and information technology is accessible to people with disabilities. IT Accessibility & Workforce Division, in the U.S. General Services Administration's Office of Governmentwide Policy, has been charged with the task of educating Federal employees and building the infrastructure necessary to support Section 508 implementation. Using this web site, Federal employees and the public can access resources for understanding and implementing the requirements of Section 508.
    URL: http://www.section508.gov
  • Title: Web Accessibility Initiative
    Description: Guidelines widely regarded as the international standard for Web accessibility
    URL: http://www.w3.org/WAI/
  • Title: WebAIM Section 508 Checklist
    Description: Provides a checklist of 508 items for HTML.
    URL: http://www.webaim.org/standards/508/checklist