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Re: Specifying foreground and background colors

From: Charles McCathieNevile <charles@w3.org>
Date: Sat, 10 Jun 2000 00:59:52 -0400 (EDT)
To: Wendy A Chisholm <wendy@w3.org>
cc: w3c-wai-gl@w3.org
Message-ID: <Pine.LNX.4.20.0006100056070.19204-100000@tux.w3.org>
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
correctly.)

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.

Charles

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 
Received on Saturday, 10 June 2000 00:59:55 GMT

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