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Re: Question Regarding Chart Patterns, Color Contrast, and Cognitive Disabilities

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From: Joe Chidzik
Date: Aug 1, 2012 6:50AM

> Could I get some feedback on which patterns you think work best to distinguish
> one pie slice from another? I have informally queried an autistic friend of mine
> who reminded me that sometimes the highest color contrast does not equate to
> the most accessible experience for him. Another friend who is color blind noted
> his preference for really high color contrast, so I'm interested in as many
> opinions as possible to find a good
> solution: http://i.imgur.com/te6tf.jpg

[Joe Chidzik] Easy to readsee colour schemes are so subjective: as you note, some vision impaired users will prefer a high contrast scheme, and we've found that some dyslexic users prefer a more pastel based theme (which they've described as having less 'glare' than starker contrast schemes). The idea of using shading in addition to colour is a good way of removing the reliance on colour, and will aid users with colour blindness or low vision.

As it is, I would say you are meeting your obligations by providing the same information in an alternative format anyway (tabular data I'm assuming).

An ideal solution, if you want to go the extra mile, would be to have a several colour schemes which users could choose from - perhaps just a high contrast one and a standard one similar to the one you linked to.

Alternatively, allow the pie charts to be interactive so that a user can toggle different sections on and off; this would allow users to hide all sections except the one they are interested in, and remove the reliance on colour alone as the distinguishing feature.

Yet another idea is to provide larger versions of the same charts; the W3C guidelines on good colour contrast are reduced for larger text as it is presumably easier to read. You could produce two versions of each pie chart; the standard size for the page, and a larger one to link to.

One thing: The W3C guidance relating to having good contrast in text, specifies that a contrast ratio of 3:1 is sufficient to distinguish links from non-link text (as an example) - http://www.w3.org/TR/2010/NOTE-WCAG20-TECHS-20101014/G183. You may want to use this as the basis for choosing a range of colours that contrast well with one another; there is sufficient room here to choose colours that contrast well, but are not too high contrast.

Joe