My natural hair color is dark brown and I want it to be light brown, so what shampoo color should I buy? ?

My hair is long and the bottom half is light blond (highlights), so I want to dye it first, and I want to be like my natural hair color (dark brown). Then I want to dye it to get one color which is light brown.My natural hair color is dark brown and I want it to be light brown, so what shampoo color should I buy? ?
Shampoo won't do any good. You need to dye to a darker color, then after a week or so, you can lighten to the color you want. I would start with a level 2 color so it fades and is not permanent to determine the color you want.