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1.4.6. Colours

Colours of Basic Map

Thematic maps show both topographic and thematic information. Since the spatial information serves merely as a locational framework or skeleton upon which the thematic distribution or relationship is hung, the spatial information should be held in unobtrusive colours.


In the following interaction part you can change the opacity of the basic map. Try to find the ideal opacity value by changing the position of the slider. When clicking the "Check Answer" button, there appears a green bar that shows the optimal values.

Colours of basic map, reproduced with the permission of swisstopo (JD072706)

Colour Ranges

In chapter 1.1.5 Colours we introduced some problems that may occur with colours on different platforms and different browsers.

In the field of thematic maps, there exists another problem with colours, since colour ranges play an important role.

(2003) recommends the following:

Clearly differentiate colours for thematic mapping, i.e. use larger colour contrasts for screen maps than for paper maps. Two close colours might appear very distinctive on a certain screen, but might be hardly discernible on another. To better differentiate succeeding thematic classes with grades of colour, you may also reduce their number (at the most 5-7 classes are recommended).


The following maps did not clearly differentiate the used colours. The map on the left used too many classes so that 10 different colours had to be defined. Therefore, the colours are too close and the human eye is not able anymore to discriminate the different colours. The map on the right used colours that are too close. As well as in the first map, the colours cannot be distinguished anymore.

Map        with too many colour classesMap with too many colour classes (Atlas der Schweiz 2.0) Colours        are too similarColours are too similar (Atlas der Schweiz 2.0)

The next two maps use clearly differentiated colours. The user can therefore discriminate the different colours with the naked eye.

Map with        clearly differentiated coloursMap with clearly differentiated colours (Atlas der Schweiz 2.0) Map with clearly differentiated coloursMap with clearly differentiated colours (Atlas der Schweiz 2.0)

Finding the right colours and number of classes

There exists a web tool for selecting colour schemes for thematic maps, most usually for choropleth maps. The tool allows to select the number of classes you want to visualise and to choose predefined colour spectra that will be applied to the given map. A few icons suggest contexts (laptop, video projector, screen, etc.) in which the particular colour scheme should work.


Explore the "Color Brewer"-tool and try to find a schema that can be used for all suggested contexts. Tip: Vary the number of classes within the same colour scheme and look what happens.

Colour BrewerColour Brewer (Brewer 2005)

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