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Color Contrast

From: Lee Roberts <uce@roserockdesign.com>
Date: Mon, 15 Apr 2002 11:02:38 -0500
To: "WCAG List" <w3c-wai-gl@w3.org>
Message-ID: <NFBBJHFEOLAGEICMIMBPAECPCEAA.uce@roserockdesign.com>
Action LR: draft success criteria for contrast

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.

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.

An excellent resource for showing what the site
will look like to someone that is colorblind.

This site has an applet that will show how colors
look to the color-blind.

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.

Lee Roberts
Rose Rock Design, Inc.
Building web sites accessible by EVERYONE
Received on Monday, 15 April 2002 12:00:21 GMT

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