We’ve talked about situations where the use of color is helpful in statistical graphics.  But one has to be careful.  Here is a recent example of a poor use of color in a line graph displayed in the Significance web site.  (This is a statistics magazine sponsored by the Royal Statistical Society and the American Statistical Association.)

Quoting the critic of this graphic, you don’t want to use 21 different colors to display results from 21 schools.  I don’t think any reader can distinguish that many colors.  Also the writer is critical of this graph from other perspectives.  The message of the graph should be obvious from the display and the caption — you don’t want the reader to be fishing around in the article to find the explanation of the graph.