You can rotate the pie chart by changing the sort order of the field on color.
In the example below, to change the sort order, I right-clicked on Ship Mode and selected Sort and used the manual sort to adjust the position of each ship mode. Another option to change the sort order is to drag the options up and down in the Ship Mode color legend. You can see the change in the sort order by looking at the order of the Ship Modes in the color legend.
I hope this helps!