I use Artec Shampoo to keep my color red (as recommended by my stylist).
You can get it at any beauty supply store.
Highlights and the lighter colors will always turn brassy on me, so I try to avoid getting highlights on top and have my stylist put it under my natural hair, so later it blends in and also the roots don't show, so you can go longer in between if needed.
Anyhow, I think it looks good on you too!
Good Luck with the next appointment and post pics!