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Re: Notes from Matt McMahon presentation on color blindness at UW

From: Doyle Burnett <dburnett@sesa.org>
Date: Tue, 13 Jan 2004 16:24:17 -0900
To: Wendy Chisholm <wendy@w3.org>, W3C Web Content <w3c-wai-gl@w3.org>
Cc: <rells@cac.washington.edu>
Message-ID: <BC29CC31.1B7E%dburnett@sesa.org>

Wendy and The List -

A few days ago Wendy and I spoke and I offered to look into a few different
things specifically related to color palettes.  I was asked to compare the
color palettes that were presented at a recent U of Washington workshop on
color blindness [1] with the color palettes from Cynthia "Cindy" Brewer [2]
and her "ColorBrewer" palette web-based tool (link from [2]).

I have found some very interesting information that may or may not be of
much use.  There is a lot of talk with regard to color safe palettes and
their usefulness by today's standards [3].

I am using a Macintosh G3 desktop computer and realize that colors across
browsers, operating systems and monitors "may" vary with regard to perceived
colors.  But, RGB values, if used correctly, should render the same value,
regardless of a users perceived notion of color.  On the Macintosh, I am
using a program called, Xproff [4] that can be used to verify the RGB, Hex
Values and other identified color values when the cursor is rolled over a
particular color on a web page, for example.

I found the palettes at [1] (figure 16) to not be accurate with regard to
what should have been the matched RGB values based upon my use of "Xproof".
On the other hand, all values from the ColorBrewer page matched the RGB
values that were presented when using Xproof.  I also found that text colors
(in this case hypertext links) are not pure colors as the color actually
fades to the outside portion of a given letter.  A value of 0.0.225
represented the darker part of a hyperlink, 152.152.225 represented the
outside edge of the text.  Please note: as the cursor moved over the text,
the color values changed and were not consistent but the overall impression
was that colors faded as the cursor moved to the outside portion.

In relationship to checkpoint 1.6, we really are not concerned about a users
ability to see and identify color - we are concerned about their ability to
see text that is presented over background colors.  The Brewer Palette and
her use of color spaces may be a valuable resource.

Hope this either helps or at least sheds additional light on the issues of
checkpoint 1.6.

[4] http://www.colorfield.com/xproof/

Doyle Burnett
Education and Training Specialist
Multiple Disabilities Program
Special Education Service Agency

On 1/9/04 12:32 PM, "Wendy A Chisholm" <wendy@w3.org> wrote:

> Hello,
> Yesterday at the AccessibleWeb@U meeting (a monthly event at the University
> of Washington) Matt McMahon,Senior Fellow in the Department of Biological
> Structure presented "Web Design for Color Blind Users."  Notes from that
> meeting are available at:
> http://www.washington.edu/computing/accessible/accessibleweb/aw010804.txt
> (Scribe =  Rick Ells).
> A "Set of colors that is unambiguous both to colorblinds and
> non-colorblinds" is referenced [1].  Where the Brewer Palette is a palette
> of acceptable color combinations, this palette identifies colors that they
> claim are "unambiguous both to colorblinds and non-colorblinds."  Further,
> they recommend
> "When combining colors from this pallet,
> - Use 'warm' and 'cool' colors alternatively.
> - When using two warm colors or two cool colors, put distinct differences
> in brightness or saturation.
> - Avoid combination of colors with low saturation or low brightness."
> I would like to see a comparison of this palette to the Brewer Palette, if
> someone is willing to make the comparison.
> --wendy
> [1] <http://jfly.iam.u-tokyo.ac.jp/html/color_blind/#pallet>
Received on Tuesday, 13 January 2004 20:23:11 UTC

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