Loss of formatting is a known problem with pivot charts. There's
information in the following MSKB article, suggests recording a macro as
you apply the formatting:

XL2000: Changing a PivotChart Removes Series Formatting
http://support.microsoft.com/?id=215904


Big Red wrote:
When using the pivot table and chart in excel, I want to format the chart to
have distinct data series formats. However, when I change the selection in
the pivot table, the charting formats return to the defaults. I want to keep
this chart formatting regardless of how many time the data displayed is
changed. Is this possible?


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html