Colour and Maps

The four colour theorem says that the areas of a map can be coloured in using just four colours. Ignore the minimalists - colour has an important part to play in communicating information held on a map. Wise colour choice and colour usage can enhance the experience of your map users. The poor use of colour can degrade you map and make it difficult to use.

Good colour choice like any design issue seems to demand a little flair and it is difficult to define hard a fast rules. Review other maps you have seen that have a similar purpose to your map. Try and decide where the use of colour has enhanced the objectives and where it has detracted from the map. This may help you decide upon how to apply colour to your specific map.

If your map is likely to be photocopied or faxed (perhaps a “how to find us” map) then this should be taken into account when designing it. A monochrome line drawing might work better than a map with coloured areas and text. Reds and blacks fax well, blues and greens do not.

If place and location names or any other form of text are an important attribute of your map then your colour scheme should take this into account. Colour contrasts could become very important to ensure that your text stands out on the relevant background areas.

Colour theory

Colour theory is a big subject and lots of technical works have been written addressing many specialist areas of application. Here you will find just a few brief points to get you started.

Colour Contrasts

There are three (so called) primary colours – Red, Yellow and Blue. There are also three secondary colours – each made by mixing two primary colours – Orange, Violet and Green. You can see these arranged below.


	Now imagine a disc with a continuous sequence of colours from each Primary to the next. These represent all of the colour Hues. Colours also have a Saturation value which represents the amount of grey mixed in and a Luminosity value representing the amount of white or black which is in the colour.

This disk represents a proportion of the colour mix values as they are reproduced by the RGB process of your screen.

You browser may have problems reproducing all of these colours. Click here to see our chart of the 216 browser safe colours.

For our purposes we should also consider White, Black and Grey as colours in their own right as well

Good colour contrast is achieved by selecting Hues that are opposite each other on the colour disc above.

Saturation contrasts can be achieved as well – a good example would be a grey contrasted with a pure red.

You can also use brightness contrasts between very dark and very light colours.

The Paint accessory that ships with Microsoft Operating systems has an excellent colour selection dialogue that illustrates how the three variables of Hue, Saturation and Luminosity define any specific colour.

Colour characteristics

Some colours have a strong cultural meaning and such meanings can vary from culture to culture. In addition some colours seem to affect our views on perspective within an image. Let us first consider the primary colours.

Red is a strong colour that moves to the foreground. Often used for warning signs and important cartographical features such as trunk routes on road maps.

Blue is conventionally used for rivers, lakes and seas on maps. It tends to recede visually.

Yellow has a visual affect which is highly dependent upon it’s background or on it’s neighboring hues. It can provide a strong contrast or appear faded and difficult to pick out.

The extreme luminosity values – Black and White both share some common characteristics. They can both represent an absence of information or neutral areas. Black is often also used to denote complex areas or to represent structures within a map detailing other geographic characteristics.

Grey can be seen as neutral – hence perhaps it’s widespread use within the MS Windows colour schemes.

Vision Impairment

If you are going to be publishing or sharing your maps widely it might be a good idea to take the high number of individuals with some form of colour blindness into account. A very useful resource is provided at http://vischeck.com You can download a java tool from there that will allow you to see your map (or any other colour image) as it would be seen by people with different types of colour vision impairment. You can then ensure that your colour choices maintain their effectiveness for the widest possible range of the sighted population.

Publishing on the Web

If you are going to publish your map on the web then it is important to select colours that will be reproduced accurately in all browsers. Click on the appropriate link to see the browser safe colour chart in hexadecimal format and where the colour values are presented as decimal triplets.