You can use the color of markers to indicate observations of interest (for example, outliers) or to color observations according to the value of some variable. The discussion in this section applies to plots that show individual markers.
The simplest use of color is to assign a color to one or more selected observations. For example, you can repeat the example of the section Changing Marker Shapes, but use color to indicate the male students.
You can color markers according to values of a nominal or interval variable. In the next example you color markers according to an interval variable. This technique is sometimes useful for visualizing trivariate data by using a scatter plot to visualize two variables and using color to visualize the third.