“If you want to proceed anyway, follow these general guidelines: "20 volume peroxide lightens your hair two levels, 30 volume lightens three levels, and 40 volume lightens four levels, says stylist Karen Wallington. And don't forget to re-dye the hair with a toner (10 volume or lower) to reduce or remove unwanted brassiness after bleaching”
How to Dye Hair Yourself at Home Without Damage