In my previous post “Colorful Expressions,” I started a discussion on the use of color and talked about its occasional overuse. Color can be a much more effective and powerful tool when it’s used sparingly and with purpose. We see this concept in images all the time. If you ever saw the movie “Schindler’s List”, there is a very powerful scene where Schindler sees a little girl wearing a red coat. The red coat is one of the few instances of color in the black and white film. The little girl's jacket is red so that she stands out from the masses. When color is used, it makes a point and an impression.
Similarly, when creating charts, you can use color effectively to make a point and impression. There are some very good techniques for using color in your charts.
Use color to:
1) highlight data (i.e. bring something to users’ attention)
2) group data (i.e. a different color per sales region)
3) convey a specific condition in the data (i.e. red = negative, green or blue = positive)
Using Color to Highlight Data
It’s a good idea to use color to focus attention on an item that is particularly relevant to the reader. Consider this chart from a Southeast regional sales conference.
In this example, the user is calling attention to the Southeast Region to show their third place status in sales revenue. It’s best to use bright and dark colors for highlighting data. You want that data to stand out and be noticed.
Using Color to Group Data
Color can be used to group data into different sets in order to show similarities or differences. In the following (fictitious) example, I compare sales revenue for three brands of running shoes across various countries.
Competition between brands is tighter in the US while Nike has a clear lead in other countries.
When grouping data, use medium shades for each group. You want each group distinct, but you don’t want one group to stand out more than others, so try and make sure their levels of intensity are equal and that there is a sense of balance among the groups.
Using Color to Convey a Condition
And finally, if you want to convey a specific condition, make sure that the color meaning will be understood by your users. In the following example, an organization is tracking their monthly billable hours for 4 major projects.
Project 1 was overbudget in Oct. but stayed within budget in Nov. and Dec.
Project 4, however, has consistently been overbudget over the three-month period.
Instead of color-coding by project, they color coded by their ability to stay within budget. Red is commonly associated with danger or warning, blue with stability, and green with safety.
Sometimes when it comes to color, less is more. Think about how you are using color in your charts. The use of color should add value to the visualization and help tell the story.
