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Does W3C Get Its Contrasts Wrong?

Filed under: Accessibility

If you follow W3C recommendations regarding colour contrast, you could be actively creating problems for as many as 10% of your site visitors.

It is estimated that as many as 1 in 10 people are dyslexic.

The current population of the UK is around 60.2 million.
National Statistics Online

This implies that the number of dyslexics in the UK is likely to be in the region of 6 million.

The number of visually impaired people in the UK in April 2005 was estimated at 1.7 million. This figure includes all those who have a visual disability that cannot be corrected by spectacles. It includes people who are entitled to register as blind or partially sighted, or who have difficulty reading an ordinary-print newspaper and whose sight restricts their mobility.
Chartered Institute of Library and Information Professionals

So, in the UK, the number of dyslexics outnumber the visually impaired users by at least 3:1.

I assume that these proportions would be roughly similar in other areas of the world.

So, why does WCAG 1.0 focus exclusively on ensuring that pages contain ‘sufficient contrast’?

2.2 Ensure that foreground and background color combinations provide sufficient contrast when viewed by someone having color deficits or when viewed on a black and white screen.

Web Content Accessibility Guidelines 1.0

Nothing about the significantly larger group who will be actively disabled by high contrasts. Not one word about the issues that can actually be created when applying their suggested algorithm.

I’m not suggesting that developers ignore colour contrast issues or consign W3C’s suggested algorithm to a category marked ‘Useless’. To do so would be to actively disable a significant number of visually impaired users.

What I am suggesting is that, if a colour theme is chosen that does conform to the W3C algorithm, an alternative, low contrast stylesheet should be provided as standard. If that’s not an option, consider lowering the contrast slightly. Yes – I mean drop the color difference below that recommended by W3C to 400 instead of 500. This would be in accordance with the range used by Hewlett Packard which recommends a colour difference limit of 400.

I’ve put together a simple test page to demonstrate this in action with examples of colour combinations that do not comply with W3C’s and similar ones that do. I, personally, find the ‘non-compliant headings’ far easier on the eye, yet the W3C recommendations do not make any allowance for bold text – a factor that should be relevant when considering colour contrasts.

I think less emphasis on higher contrasts, greater allowances for bold text and a slight reduction in the threshold for color difference will result in pages that will be slightly easier for the larger group of dyslexic users to read whilst not severely impacting on the smaller group of visually disabled users. A positive ‘side effect’ may well be that users without any special needs will find the slightly lower contrast pages less tiring on the eyes – thus enhancing overall readability.

Published: October 3rd 2006


  1. Isofarro

    Interesting thoughts. Just so I’m understanding this – does the problem of too high a contrast prove to be a barrier to all people with dyslexia? Also, is it being said that all colour schemes that meet W3C’s colour contrast will present a barrier for people with dyslexia (and thus we need to always have a supplementary stylesheet that consistently needs to fail the colour contrast tests)?

    Is a high colour contrast making text too sharp, and thus creating a situation where the text itself seems to move/wobble/shimmer, or the spaces between the text to dominate more? I know one of my friends finds that anti-aliased/shadowed text causes her problems.

    Thanks, Mike

  2. Joe Clark

    I’m sure you meant “Does W3C Get Its Contrasts Wrong?”

  3. James

    I’m reporting you to the society for apostrophe abuse.

  4. Black Widow

    Joe: Yes – you’re absolutely correct!

    James: My apologies. I don’t have a problem with punctuation but my fingers are dyslexic (in other words, I’m a lousy typist and an even worse proof reader). :-)

  5. Black Widow

    Mike: Good points which I’ve now hopefully discussed further in More On Dyslexia

  6. Spider Trax » An Alternative Colour Contrast Analyser

    [...] Following my comments in Does W3C Get Its Contrasts Wrong?, I decided to develop an alternative colour contrast analyser that took into account some of the points I’d raised. [...]

  7. Isofarro

    Mel, thanks for an awesome and comprehensive answer! I’d suggest lifting that comment out into an article by itself, its chockfull of useful and insightful information.


  8. Spider Trax » More On Dyslexia

    [...] A number of questions were raised following Does W3C Get Its Contrasts Wrong?. The following was orginally posted as a comment follow-up, but, since it’s rather long, I’ve re-posted it here. [...]

  9. Pat Rees

    Another very important issue with high contrast text, such as black on pure white, is that text letters will break up when enlarged with low vision technologies such as ZoomText. An ever so slightly less white background, such as #FDFDFD, will reduce the way text is pixelated and thus made more readable in assistive technologies like ZoomText. With high contrast, letters lose their rounded edges and become unrecognizable in ZoomText. Even though a color and background meet the acceptable range, it does not guarantee that the combination will be readable when used with ZoomText. I found that I had to Zoom test each of my color combinations to make sure it would work, but overall the higher the contrast the more likely it would break up.

  10. Jermayn Parker

    On your test page example I personally found that the second example “Yellow Background: Compliant” was the worst of the three as it hurt my eyes when reading it. The other two examples were better as they were not as sharp and easier on my eyes.

  11. Mike Cherim

    Outstanding observation, Mel. I cannot comment on the technical merits of your argument, but from a purely subjective point of view I’d certainly have to agree. I have neither poor vision or dyslexia, but I do find a somewhat subdued level of contrast much easier on the eyes and it makes the reading easier and more enjoyable for me, especially with a screen presentation. Based on these personal preferences I typically publish a darkish gray text on an slightly off-white background which is slightly non-compliant.


  12. Gill Lucraft

    I have to agree with this. I’ve spent the last week trying to comply with WCAG contrast and brightness which is not a problem but as soon as you add luminosity you’re either completely restricted colour wise or you get a headache. Have they actually tested their recommendations?

  13. Black Widow

    I have absolutely no idea but the feedback I’m hearing suggests that a number of designers have been using the Hewlett Packard thresholds for some time – yet have not received any complaints with regard to lower contrasts.