ColorBrewer.org: An Online Tool for Selecting Colour Schemes for Maps

Colour plays a central role in thematic cartography. Despite this, using colour effectively on maps is surprisingly difŽcult and often exceeds the skill and understanding of novice mapmakers. On the one hand, a ‘good’ colour scheme needs to be attractive. On the other hand, the colour scheme must also support the message of the map and be appropriately matched to the nature of the data. Moreover, colour schemes that work for one map (e.g. a choropleth map of income) will not necessarily work for another (e.g. a map of dominant commercial sector by county). Relying on the same colour scheme for all thematic mapping needs is a mistake. Unfortunately, many novice map makers have become conditioned to use the default colour schemes built into commercial mapping and GIS packages and sometimes are even unaware that they can change those default colours. If colour schemes are not carefully constructed and applied to the data, the reader may become frustrated, confused, or worse, misled by the map. An understanding of how to manipulate the three perceptual dimensions of colour (hue, saturation and lightness) is required to create attractive and logical colour sequences for thematic maps. These dimensions are three of the visual variables or basic ‘building blocks’ of graphics (Bertin, 1983). Nearly a century of colour theory development combined with perceptual testing has allowed us to better understand how individuals perceive and understand colour. From a semiotic perspective, colour works as a ‘sign vehicle’ when the map reader is able to understand that a speciŽc colour on the map represents or stands for something in the real world and that multiple occurrences of that colour stand for the same kind of thing (MacEachren, 1995).