Hiya, I was a hairdresser, now I only do friends & family hair.

There's 2 options

1. Go to a hairdressers and ask them to put a toner in your hair, however this will cost you a fair amount of money & time.

2. What I use at home for myself is Delorenzo Nova Fusion colour care shampoo Silver, It is expensive around $25 a bottle but is worth it, it lasts ages & you dont need much when you use it, you can get it from Price Attack, Salons, and hairdressing wholesalers. RPR make a good one as well. You are better off getting a salon brand as it is design for what you are trying to do, the supermarket brands are designed to maintain the colour, not fix it.

The first day wash your hair with the shampoo & leave in about 3mins, (make sure none gets on your shower walls coz it will stain, its dark purple) rinse & follow with conditioner (you can use any conditioner, it doesnt have to be that brand).
Then everyday thereafter use it as a normal shampoo (so lather & rinse, don't leave in) until you get the desired colour you are after.
Then just use it once a week or once a fortnight.

Hope this helps, good luck