Hi Bob,
Yes, you can change the Legend formatting. For example, you can only use: <label>
In the Pivot >> Data Groupings >> Values >> Legend – Format: field, simply label <label>. It will take the label from the Pivot >> Data Groupings >> Values >> General – Label: filed (which can also be an expression).
You can also take a look at the Help Documentation: http://helpsharepointvision.nevron.com/
Chart > Data Model > Data Point Formatting Commands