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I've been given a very limited colour palette to work with for a number of charts. Because the palette is limited, it's been suggested that using the same colours but with patterns such as stripes (horizontal, diagonal, vertical) or other simple patterns could address the problem. Is this likely to cause problems with accessibility?

Example shown below. The charts could be pie, bar, donut or indeed any chart type:

enter image description here

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Could you give an example, images, colours? you can always use shades of the same colour to help the communication or make the a little interactive - on hover. It's hard to understand the problem. –  Igor-G Jan 31 at 10:30
    
Please give more context; what are you using the colours for? What kind of charts? For example, if you are using them as blocks of colour on a histogram, that is a different matter to using them as background for text. –  Alnitak Jan 31 at 10:32
    
Your stripe patterns already give me visual hallucinations :D –  Leths Jan 31 at 11:09
    
@Leths that's kind of where I'm coming from! But I'm really looking for any evidence that it causes a problem, e.g. with accessibility or for people with dyslexia. –  Peter Jan 31 at 11:15
    
@Peter this is terrible! use 1-2 hues(colours) on black/white background and reduce opacity by 10%, same hue(colour) and nice effect: peltiertech.com/images/2011-05/piesbyparesh75.jpg because this is pretty much what you are doing by adding lines –  Igor-G Jan 31 at 12:14
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You can play with:

  • Brightness/Darkness scale (because even color-blind can make this difference) -> Make sure that the difference of brightness is significant otherwise it is difficult to identify.
  • Textures (here it is bad because the rows are too dense-> Visual hallucination. Try play with bigger symbols)
  • Labels directly on the chart (user can identify the sections with associated label instead of colors-> need to have good contrast between label and background)

I just found another (bad) example from the internet:enter image description here

This is a bad example to give you more ideas. If you go for textures it decreases label readability, so either chose to play with textures, either to play with labels directly on the chart. As you can see, the texture used in this example gives less hallucinations because the spacing is more important.I believe you could remove this visual effect with larger lines/symbols.

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The visual hallucination you refer to are called moire patterns. And yes they are quite difficult to avoid when using line hatching. IMO point textures are bit easier on the eyes. A simple solution to the labels would be to have the label have a non-transparent background with a slight buffer/halo (or have the labels outside the pie). –  Andy W Jan 31 at 14:14
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