I had wishy washy light/med warm brown hair, which was lighter a the roots after colouring my hair - I could never find a box colour that would cover my 'golden' roots & reduce the warmth in my hair.
Then I remembered using the Shwarzkopf poly tint colours a few years ago & then being quite good so I got two boxes - a natural brown & a medium brown £1.95 each from Wilkos.
I nearly all the medium brown to my roots, left that on for 25 mins then applied all the natural brown to the rest of my hair & left the whole lot on for about ten mins or so.
The instructions says to shampoo out but I didn't, you don't get a conditioner with this colourant so you use your own.
And the result is amazing, my hair is super shiny & the exact shade of brown I've been after, a neutral med brown, with no reddish tones & my roots are a nice med brown, all blended in. A fab colour, I'm going to stock up in case they discontinue!