Legend for pie chart from pivot table - repeating subcategory

I was hoping somebody could help.

I attach a file of my data, pivot table and resultant pie chart. I want a way for the legend to just have the categories, 'blue', 'red' and 'yellow', and not to have 'big' in front of each. Is it possible?

The big is the sub-category that I am sorting for in the pivot table.

Thanks for your help!