- From: Lee Roberts <uce@roserockdesign.com>
- Date: Mon, 15 Apr 2002 11:43:37 -0500
- To: "WCAG List" <w3c-wai-gl@w3.org>, "john_slatin" <john_slatin@forum.utexas.edu>
- Message-ID: <NFBBJHFEOLAGEICMIMBPGEDACEAA.uce@roserockdesign.com>
MessageOne link slipped by me. I'm adding it now so that people will have an understanding as to why dark backgrounds with light text should not be used. http://www.msdn.microsoft.com/library/default.asp? url=/library/en-us/dn_voices_hess/html/hess0814200 0.asp Please refer to the section entitled "Pump up the Contrast". This section decribes the problems with contrast and how contrast works. Yes, Catherine Rigdon's information is useful. It may be helpful to refer to it. Lee Roberts -----Original Message----- From: john_slatin [mailto:john_slatin@forum.utexas.edu] Sent: Monday, April 15, 2002 11:11 AM To: 'Lee Roberts' Subject: RE: Color Contrast Thanks for these links, Lee. This is very helpful. Another good resource is the site "Safe web colours" by Catherine Rigdon of British Telecom (hence the "u" in "colours"). The site offers a number of color charts and sample palettes, with illustrations that show how different colors appear to people with different types of color-deficient vision. Also good advice about design issues (including the advice Lee lists several times about choosing complementary colors, i.e., from opposite places on the color wheel). At http://innovate.bt.com/people/rigdence/colours/ One small caveat about the success criteria: it may not *always* be a good idea to require that text be darker than the background-- for some users, the effect of text illuminated against a dark ground (e.g., yellow on black, white on black, etc.) is more readable. John Slatin -----Original Message----- From: Lee Roberts [mailto:uce@roserockdesign.com] Sent: Monday, April 15, 2002 11:03 am To: WCAG List Subject: Color Contrast Action LR: draft success criteria for contrast checkpoint. http://www.dai-sho.com/colorblindness/ The most common color perception problems are with certain color combinations such as yellow on green, green on red, red on green, blue on red, red on blue, and red on black. The site above goes on to explain that using colors from the same end of the spectrum is difficult for people with colorblindness to tell the difference in the colors. Additionally, light colors on dark colors are difficult to read as there is not enough area in the light areas to provide enough of a contrast. Using varying shades of the same color also creates problems. If you intend on using red and green , make sure that when one changes to the other, that there is a suitable blinking, noise text or something to augment it. Please stay away from pastels, washed out colors, low intensity colors, and color combinations from the same part of the spectrum. http://www.lighthouse.org/color_contrast.htm This site suggests using colors from opposite ends of the spectrum. Additionally, it has several color charts that depict the difference in color spectrum and contrasting colors. There is a great deal of information on the subject on this page. http://www.vischeck.com/vischeckURL.php3 An excellent resource for showing what the site will look like to someone that is colorblind. http://www.internettg.org/newsletter/mar99/color_c hallenged_applet.html This site has an applet that will show how colors look to the color-blind. http://www.msdn.microsoft.com/library/default.asp? url=/library/en-us/dn_voices_hess/html/hess1009200 0.asp?frame=true Excellent color comparisons. Success Criteria: Achievement of color contrast will be based upon the following areas: 1. Text should be darker than the background. 2. Text and background will have sufficient contrast to distinguish the differences. 3. The saturation of colors will be sufficiently different to distinguish the differences. 4. The hue of the colors will be sufficiently different to distinguish the differences. 5. Color combinations of yellow on green, green on red, red on green, blue on red, red on blue, and red on black will not be used. 6. Use a light grey or off-white instead of plain white as the background. Sincerely, Lee Roberts Rose Rock Design, Inc. Building web sites accessible by EVERYONE http://www.roserockdesign.com
Received on Monday, 15 April 2002 12:41:14 UTC