Highlights and shampoo

[livvyliv]

I've recently had a few highlights in my brown hair to blend in with the grey.I asked for caramel/toffee tones but tbh they're a bit blonder than that.is there anything I can use to tone them down and what is the best shampoo to stop them going straw/brassy?
Thanks

Don't know about toning down without putting another colour on top, but I use this to keep my blonde bits blonde.