GIS Tips – Be careful about your colours

You know when you have something to say, then realise that it’s not as easy as just putting it down on paper, well……I love to believe that I am a cartographer, though compared to Gretchen Peterson I am possibly more akin to a child finger painting the Mona Lisa.
My problem is that I have mild obsessive compulsive behaviour issues, if I see something that bugs me, it eats away and consumes my soul, you’ll find many of the great GIS users have a mild OCD…I mean, you’d have to, to get so wound up over a vertex not snapping or a grid being 2cm out.

My question is, does anyone stand back and look at their maps anymore? My OCD is going into overdrive with some of the maps I have seen recently, not the quality or the detail, this has improved ten fold in the past few years, my issue lies with the colour choices.

Have a look at the map below, okay, it’s quite humorous, though what are your initial thoughts about the colour? What does red signify? What would you EXPECT?

What do these colours say?
What do these colours say?

In my opinion red has always been associated with DANGER or RISK (okay it could be the cartographer having a joke with us)…..

Now, have a look at the map below and tell me which area is of most importance:

Which area is most important?
Which area is most important?

You see in this example, just by using red, amber, green (and blue), the author has subliminally alluded to importance just by the colours they have chosen.

Right, last one, this time I want you NOT to think about rivers or streams:

Are they streams?
Are they streams?

In this example the routes are highlighted in blue, which, if you look quickly, appear as rivers or streams until your brain has had time to decipher what is going on here.

And I think that hits the nail on the head, your brain is predisposed and trained to recognise certain things. Danger is red, water is blue, mud is brown and land (as in mapping), is green. American philosopher Daniel Dennet has even proposed that we, as humans, are genetically predisposed to recognise things.

The fact that we are predisposed in this way means that we need to be more intelligent in our cartography, this doesn’t mean we have to create everything in greyscale, in fact, quite the opposite! This means that we can have some real fun with it – Have a look at these two examples of the same information:

Cannabis Use Cannibis_goodThe top map is cartographically correct, it looks okay, though the bottom map is attractive to the eyes, why?….Subliminally are you making the association with marijuana (also called weed) of GREEN? Below is a map showing ‘Cord Blood Legislation Enacted’


My question here is; would the map have worked if the author used any other colour than red?…I’m not too sure, after all, I am seeing blood and thinking RED.

Of course, it is not always possible to produce a map which is based on our predisposed ideas, I often create legal maps and figures which I am sure would not go down well if I used heavy amounts of red for areas at risk….especially when we are trying to show that the project has little risk. The fact that I am considering how a client or consumer may think about the colours already puts me one step ahead.

It obviously comes down to the TYPE of map you are creating but definitely keep this all in mind when creating your works of art.

One colleague of mine had a big thing against me using pink, especially on any navigation charts. If you have ever seen a navigation chart, they are very clever with their cartography and leave very few colours for applying data to. Many times I would have to show fishing vessels and would be limited to either blue (not good when the sea is blue) or pink (a very good contrast for the blue)….but as my colleague pointed out…..THEY would be the ones physically showing a bunch of butch fishermen where we believed their vessels were moving and using pink was asking for a fight….

Choose your colours wisely

Nick D

1 Comment

  1. Great discussion of color connotations. Regarding pink, you could point out that pink–especially light pink–is actually quite common on historic navigational maps. Here’s an 1831 map of the U.S. with bold pink. Here’s a map with some mild pink in it from the 1700s, Russia:

    Some more thoughts on pink are (1) that pink was actually considered a “boy” color back a few hundred years ago since it was like a light red, (2) genderization of colors seems rather ridiculous on the face of it, and (3) boys are adopting pink and purple in their clothes and shoes more and more these days (though who knows whether the trend will continue or not).

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