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Depending on what you read, 7 to 15% of the general population has some form of colour blindness.

Can this be accounted for in map designs and, if so, how?

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    I second Swingley's answer. Unless you know with 100% certainty that your maps (soft or hardcopy) are going to be consumed by a group without any accessibility problems, you should try to accomodate them. After all, the purpose of cartography is to communicate a message. You probably don't want your message to be misunderstood if you can help it.
    – Tim Rourke
    Oct 25, 2010 at 16:43
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    This question is also applicable if you know your medium will be black,white, and grey scale. Or at least the answers would be very similar if the question were how to convey a map without colors.
    – Andy W
    Oct 25, 2010 at 17:09
  • I used to work with a GIS Analyst who was quite severely colour blind. Im talking pink oceans and all sorts.
    – jakc
    Oct 26, 2010 at 9:01
  • wow, 4 great answers in a single day. Thanks folks. I wish I could mark all of them 'accepted' :)
    – matt wilkie
    Oct 26, 2010 at 16:07
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    I think you should open this as a new question. It will get more press, and you can identify any particular aspects of the paper you would like to discuss more specifically (in fact the more specific you get the better responses I suspect you will get, as opposed for just asking for generic feedback).
    – Andy W
    May 6, 2011 at 20:11

13 Answers 13

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One of my clients is colour blind, and when I make maps for him, I use vischeck.com to check my work. You can upload your own image, and it will return a processed version of it that shows what it will look like to colour blind folks.

It has options for various types of colour blindness, and is pretty educational to boot.

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The large majority of the work I do is for a very limited audience, so no, I do not usually account for colorblindness. If you do need to accommodate colorblindness, color brewer has a "colorblind safe" option that is helpful.

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  • +1 for colorbrewer - this resource is a must! And it's now nicely integrated into ArcGIS and R.
    – radek
    Oct 25, 2010 at 17:26
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    It is also built into uDig
    – Ian Turton ♦
    Oct 26, 2010 at 16:28
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    +1 colorbrewer is also available in QGIS since v1.4
    – underdark ♦
    Oct 26, 2010 at 22:13
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I am slightly red-green colourblind (in that I can still see red and green fine, but have difficulty with say a red and green line next to each other). Does make it a bit easier for me to make maps for people that are red-green colourblind.

In addition to color brewer and vischeck mentioned above, the GIMP has colourblind filters built in so you can adjust images as part of post processing. Photoshop has the same kinds of filters if you have access.

Lastly the ESRI Mapping centre has a set of styles for download that include a colour set suitable for colour deficiency.

Hope that helps!

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  • +1 for GIMP and Photoshop filters. Really interesting to see.
    – underdark ♦
    Oct 26, 2010 at 22:17
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This is a very good topic.... and there is software out there for cartographers.

Color Oracle is a colorblindness simulator for Window, Mac and Linux

http://colororacle.cartography.ch/index.html

The system-wide menu quickly converts your art into a palette that simulates what colorblind people see.

Covers different aspects of colorblindness

Deuteranopia, protanopia and tritanopia.

"Designing maps for the colour-vision impaired" [PDF]

http://colororacle.cartography.ch/design.html

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  • Thanks for this link. A big help for the map I'm currently making.
    – maning
    May 30, 2011 at 2:56
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Gretchen Peterson has written a few books/booklets on GIS cartography that could be useful resources.

She also references the website:

  • ColorSchemeDesigner - which has an interactive visualizer that emulates what a colorblind (many varieties available) user would see.
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we were exploring this topic and produced a draft document (link below) which maybe of use...I would appreciate any feedback you have to improve this document

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0BymNZZfQQ3a0NjQxOGVmMjYtNzE5NS00ZGI1LTg4NDMtZTFkYTg0NDQ1YmVi&hl=en&authkey=CJmi15oE

--- ADDENDUM ---

As requested here are the main tips...a lot of them are also listed in other peoples responses.

Tips for making maps for colour-blind people

  1. Exaggerate lightness differences between foreground and background colours. Avoid using colours of similar lightness adjacent to one another, even if the hue or saturation is different.

  2. Minimise the number of colours used in thematic maps.

  3. Use a colour scheme recommended at http://colorbrewer2.org/ such as one of the diverging schemes above. They have schemes recommended for color blind use.

  4. Vary the lightness of the colours used. The intensity differences visible for persons who are colour-blind.

  5. Use thicker lines so the eye can interpret the colour better.

  6. Where possible, make stylised maps with less geographical information. The reduced information means there are fewer colours to distinguish.

  7. Use white halos around lines as this helps keeping the colours distinct and reduces the confusion when the lines intersect.

    • Install http://colororacle.cartography.ch/ which allows you to change the whole display to the 3 main types of colour blindness to check if the scheme used is ok.
    • Check http://colororacle.cartography.ch/links.html for other software that can be used.
    • Read http://jenny.cartography.ch/pdf/2007_JennyKelso_DesigningMapsForTheColourVisionImpaired.pdf
    • The Conservation template project is addressing this same problem for a different reason: If you are using a basemap with a colour scheme then the thematic map you design to lay over that basemap cannot use those same colors. In looking at the maximum information you can carry without relying on colour we are spending time looking at symbol texture and pattern, using similar methods from black & white photo-interpretation. These line symbols only work well within a limited scale range, in this case 20k to 1k. Then you have to shift to a different set. They all rely on the line offset and layer properties to create the 3 bands, but that technique may not scale well in dynamic feature services so if we can find a design that works we may look at other server options like caching. Charles Convis, ESRI Conservation Program Coordinator.
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    Thanks for the reference George, that looks like a good document, though I only skimmed it as I'm pressed for time today. To improve your answer you could include an executive summary (precis) of what the document is about, it's primary ideas (c.f.microcontent)
    – matt wilkie
    May 12, 2011 at 16:07
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Fairly old question, but as I'm horribly colourblind myself, I'll throw in my 2¢...

A quick and dirty method is to print the map out in greyscale. If you can't tell the difference between two shades (and they're similarish colours on the coloured map), then I (and, I assume, other colourblind users) may not be able to distinguish between them on the coloured map.

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A new about Ordnance Survey work about color blind maps http://www.wired.co.uk/news/archive/2011-05/11/ordnance-survey-cvd-maps

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A new feature in the current versions of QGIS (introduced in 2.4) was a preview test for different types of colour blindness.

This blog article from earlier in the year explores it a little.

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Some more general resources for online work are the W3C's Web Accessibility Initiative, an implementation of a Contrast Analyzer, and The Shaw Trust's Web Accessibility Services.

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I found the colarhexa.com website useful in identifying how a user would experience a colour you pick.

To use it just select or search for a colour by name, hex code, rgb, etc. and then use the blindness simulator link (or just scroll to bottom of page), example for green.

If you know the hex code, just embed straight to the url like so: http://www.colorhexa.com/00ff00#blindness-simulator

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    Looks like a good site, thanks :) --- Link only answers aren't very useful, inevitably the links break and then it turns into just one more dead end. A link with a name and context however is much more useful. See my edit for an example (and it is just an example, please feel free to re-work).
    – matt wilkie
    Dec 20, 2013 at 19:47
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There is a good article in Cartographic Perspectives:

Color Design for the Color Vision Impaired, Bernhard Jenny and Nathaniel Vaughn Kelso

There is quite a lot of theoretical considerations and practical tips. It utilizes Color Oracle tool mentioned by GeorgeC.

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User colorbrewer from http://colorbrewer2.org/. They have options to choose colorblind safe images.

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