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Re: Specifying foreground and background colors

From: Wendy A Chisholm <wendy@w3.org>
Date: Tue, 13 Jun 2000 21:07:11 -0400
Message-Id: <>
To: Charles McCathieNevile <charles@w3.org>
Cc: w3c-wai-gl@w3.org, w3c-wai-ua@w3.org, w3c-wai-er-ig@w3.org
At 12:59 AM 6/10/00 , Charles McCathieNevile wrote:
>Assuming a particular colour combination is a user's default and that
>therefore it is only necessary to specify colours for things that are not the
>default is a mistake.
>(particularly for accessiblity reasons they may choose
>something else, although there may be other reasons. I don't know that it is
>a reason not to include the technique, as the way to specify thinigs

My main question is not "should we include this as a technique."

Rather, my question is, "what is the accessibility rationale for this 
technique."  I did not see any, thus did not include any in my proposal.

I think the rationale is "good design."  Regardless of whether I choose a 
high-contrast background and foreground color combination (white and dark 
red), if the user only selects a foreground color (white) current user 
agents will not select a high contrast background color.  They will display 
the author set background color (white) and the user set foreground color 
(white).  The user will have to select a foreground color as well.  In some 
browsers, the user could select "high-contrast mode" where the browser 
selects both the foreground and background colors.  For example, yellow 
text on a black background.

>Maybe we should ask the ER or UA groups to look in more detail at the issue
>of ensuring contrast? Most User Agents allow a choice of colours, although
>most do not automatically pick a contrasting colour where there is a conflict
>or semi-specified colour scheme.

I think this is a UA issue and have CC'ed the UA working group.  Chris 
Ridpath recently published results of a color study, so I have CC'ed ER as 
well.  Refer to the techniques for Checkpoint 2.2 in the 26 April 2000 
working draft of AERT [1].

Since there do not appear to be any objections to my proposed edit of the 
CSS techniques module, I will make the appropriate changes.


[1] http://www.w3.org/TR/AERT#color-contrast

>On Thu, 8 Jun 2000, Wendy A Chisholm wrote:
>   I have two questions in relation to this issue:
>   1. will user agents automatically make adjustments for background or
>   foreground color if the author specifies a good combination but the user
>   only specifies one or the other (foreground or background but not
>   both)?  It is my experience that user agents do not.
>   2. I intend to include this in the techniques document, but would like a
>   rationale.  It seems that the rationale is good design rather than an
>   accessibility issue since the answer to the first question seems to be 
> "no."
>   If there is no disagreement, I propose editing section 5 (Colors) of the
>   CSS techniques module to read:
>   <blockquote>
>   Use these CSS properties to specify colors:
>   'color', for foreground text color.
>   'background-color', for background colors.
>   'border-color', 'outline-color' for border colors.
>   For link colors, refer to the :link, :visited, and :active pseudo-classes.
>   Note that when a background color is specified, specify a high-contrast
>   foreground color and vice-versa.
>   Ensure that information is not conveyed through color alone. For example,
>   when asking for input from users, do not write "Please select an item from
>   those listed in green." Instead, ensure that information is available
>   through other style effects (e.g., a font effect) and through context
>   (e.g,. comprehensive text links).
>   For instance, in this document, examples are styled by default (through
>   style sheets) as follows:
>   They are surrounded by a border.
>   They use a different background color and also specify a high-contrast
>   foreground color.
>   They begin with the word "Example" (or "Deprecated Example".
>   They also end with the phrase "End example", but that phrase is hidden by
>   default with 'display: none'. For user agents that don't support style
>   sheets or when style sheets are turned off, this text helps delineate the
>   end of an example for readers who may not be able to see the border around
>   the example.
>   </blockquote>
>   --wendy
>   At 12:59 AM 6/7/00 , Wendy A Chisholm wrote:
>   > From the issues list:
>   >
>   ><blockquote>
>   >Issue raised by: Philip Newton - 7 May 1999
>   >Issue:
>   >If the author specifies a background color, they should also specify the
>   >foreground color (and vice versa), otherwise if the user has selected a
>   >particular foreground color that does not contrast well with the author's
>   >background color, the page will be unreadable.
>   >
>   >Proposed Resolution
>   >While the user should be able to adjust preferences on the user agent, it
>   >is good design. Therefore, it seems to make sense to discuss in 
> techniques doc.
>   ></blockquote>
>   >
>   >Even if the author selects both a background and text color, if the user
>   >selects a foreground color that does not contrast well with the author's
>   >background color then what can you do?  If the user only selects one 
> color
>   >but the author has selected both foreground and background, the user 
> agent
>   >will not automatically use colors that contrast well, will it?
>   >
>   >I agree this is good practice but I am not sure that this increases
>   >accessibility.
>   >
>   >Thoughts?  Do people have experiences that support the proposal?  Does
>   >someone have a good test page for this?
>   >--wendy
>   >--
>   >wendy a chisholm
>   >world wide web consortium
>   >web accessibility initiative
>   >madison, wi usa
>   >tel: +1 608 663 6346
>   >/--
>   --
>   wendy a chisholm
>   world wide web consortium
>   web accessibility initiative
>   madison, wi usa
>   tel: +1 608 663 6346
>   /--
>Charles McCathieNevile    mailto:charles@w3.org    phone: +61 (0) 409 134 136
>W3C Web Accessibility Initiative                      http://www.w3.org/WAI
>Location: I-cubed, 110 Victoria Street, Carlton VIC 3053
>Postal: GPO Box 2476V, Melbourne 3001,  Australia

wendy a chisholm
world wide web consortium
web accessibility initiative
madison, wi usa
tel: +1 608 663 6346
Received on Tuesday, 13 June 2000 21:07:00 UTC

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