Colour and shades of grey

Simple bar charts (of the type shown in this section) display their information as effectively in black and white as in colour.

In pie charts however, the slices corresponding to the categories touch each other, so it is more important that they can be easily distinguished. If there are more than 3 or 4 different categories, colour is best to distinguish them. There is no overhead to use colour in web-based publications, but it is more expensive to print colour on paper so different shades of grey are often used in printed pie charts.

Shades of grey are difficult to distinguish if there are many of them, so the category names are often printed adjacent to the pie chart slices instead of in a separate key.

In publications that do not use colour, extra care must be taken to clearly identify the segments of pie charts.


Next billion population

The world population is projected to increase by just over 1 billion between 2000 and 2015. The pie chart below describes the regions of the world from which these extra people will come.

It is fairly easy to match the slices of the pie chart to countries when they are drawn in colour. Use the pop-up menu to draw the pie chart with different shades of grey. The regions are now harder to identify.

Types of student in tertiary education

The pie charts below were published to describe the students in three types of tertiary education college in New Zealand in 2002. Note how the segments of the pie chart are labelled.

Although the individual pie charts are clear, there is a major problem with the way that they are shaded. There is no consistency in the ordering or shading of categories in the different pie charts. For example, 'full-time female' is represented by black in two of the pie charts but grey in the third. If the same ordering and shading had been used in all pie charts, it would have been much easier to understand the differences between the three types of college.

If several groups are being compared, it is essential that the same colours and ordering are used for the display of each.

Comparison of different groups will be discussed more fully in a later section.