Shampoo question

Hey Ladies, what's the best shampoo for multi colored hair ? I have an appointment soon to have white blonde highlights put in my dark brown fauxhawk and i'm also thinking about getting some dark cherry/dark auburn lowlights put in as well. When I had white blonde highlights before I used "Matrix Essentials : So Silver " but now that i'm going to be having another color put in is it still okay to use a purple shampoo? If so what is the best one? If not what you recommend ? I still have some of the "so silver" left but its over a year old and i'm going to be getting some new shampoo anyway and wanted to get the best thing.


Thanks !