It’s easy to spend a lot of time formatting a chart, but if you’re like me you try different things and in the process you want to go backward and forward testing different changes. You may even want to go back to the original theme or part of the original theme. Here’s how to go back to the original theme’s formatting for a specific element or for the entire Excel chart.
Right-click on the Excel chart element you want to change back to the original theme, then choose Reset to Match Style. If you want to undo and return to the original theme for the entire chart, then select the entire chart, right-click, and choose Reset to Match Style.
This works even if it wasn’t the last change you made.