Hello Cherifa,
It is possible to do conditional formatting of a Pivot Table though there can be some difficulties if you want to change the layout of the table drastically and you lose it if you delete the Pivot Table.
The attached file contains a table that has been formatted this way. You should be able to look at the Conditional formatting rules and work out what you might need to do in your case.
PivotCondFormat.zip
If you want to use VBA, you could have a read here http://peltiertech.com/pivot-table-conditional-formatting-with-vba/ and this might help you along the way.
Regards
Harry