How to choose a map's colours
Colour decides what you see first on a map and which wall it suits. This guide explains the conventions of cartography, how many colours to use, how to choose the paper and how to make a map that reads well on screen, on paper and for everyone.
The traditional colours
Cartography has used the same colours for centuries, and for good reason: blue for water, green for vegetation, brown or ochre for relief and black or dark grey for what is built, streets and buildings. Anyone reads a map like that without a legend.
It is a good starting point, especially on a topographic map, which has to be understood. PlotMyMap's topographic style follows those conventions: earth-toned contours, blue water, green forest and red buildings, like hiking maps.
Breaking the conventions works too, but on purpose. A decorative map can be all one colour, or use pink for the water if it suits the wall. What does not help is going halfway: if water is green and forest blue, the eye gets confused.
Fewer colours, better map
The most common mistake is using too many colours. Each new colour asks for attention, and a map with ten different tones has no lead.
A simple rule: one or two strong colours and the rest neutral. For instance, water in deep blue, buildings in coral red and everything else in greys or the ink colour. That way the eye goes to what matters first.
Single-colour maps, all black on white or all white on blue, are the most elegant and the easiest to match. The hierarchy then comes from line weights and hatching: water with shore lines, parks with scattered marks and buildings with straight lines tell themselves apart without any colour.
In PlotMyMap the colour themes change every colour at once with palettes designed to go together: Classic, Black ink, Sepia, Coral, Night and Blueprint. They are a good place to start before touching anything by hand.
The paper is a colour too
The paper colour covers the most area, so it sets the tone of the whole map. Pure white feels technical and modern; cream or ivory, warm and like an old print; light grey, sober.
Choose the line colours with the paper in mind. On cream, browns and muted blues look natural, like an engraving. On pure white, bright colours look cleaner. On a dark background, lines have to be light, and very saturated colours vibrate.
If you are going to print, remember the paper colour comes from ink: a dark background covers the whole sheet and uses a lot of ink. If you are going to plot or engrave it, the paper is the real one and the map's background colour is only a preview.
Contrast: make it readable
A map has to read at the distance it is seen from. Thin lines in light colours (a yellow, a pale green) vanish on white paper, especially on a poster seen from a couple of metres away.
A quick check: look at the map on screen, step back or squint. Whatever disappears has too little contrast. If it is something secondary, like footpaths, that may be fine; if it is the river that shapes the city, darken its colour.
Hatching has its own colour, separate from the outline: a building can have a dark outline and hatching in a lighter tone of the same colour. The area looks filled without weighing as much, a very classic cartographic touch.
And think about what goes on top of what. In PlotMyMap's map elements, order matters: what is above covers what is below. A strong colour on top of everything sets the hierarchy better than any colour trick.
Dark maps
A map with light lines on a dark background, like the Night theme, is striking and very modern. It works best on light walls, on screens and in cities with a dense street pattern, which look lit up.
On a dark map, less is more. Very bright colours on black are tiring; better slightly muted tones, like amber for buildings or light blue for water, and off-white rather than pure white for streets.
Blueprint is another kind of dark map: everything in light tones on deep blue, like old architectural plans. It really suits a city with a regular grid.
Colours for everyone
Roughly one in twelve men has some form of colour blindness, almost always trouble telling red from green. On a map where parks are green and buildings red, the two areas may look the same colour to them.
There is no need to give up those colours: just make sure they are not the only thing that tells one thing from another. If parks carry a different hatching from buildings (scattered marks against straight lines, for example), the map reads without relying on colour.
Varying lightness, not just hue, also helps: a light green next to a dark red still separates in black and white, which is roughly how someone with strong colour blindness sees it. If you print a greyscale proof and the areas still stand apart, the map works for everyone.
Saving your palette
When you land on a combination you like, save it in My styles: it keeps the map type, colours, elements and typeface, and you can apply it to any other place. It is the way to make a series of maps with the same feel, say the cities you have lived in.
If you get lost changing colours, “Back to the starting style” undoes everything you touched and returns to the style's colours.
Before printing a large size, ask for a small proof: screen colours never come out identical on paper. The printing guide explains what to expect.
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