How do I do it?
For at home dyeing, to get the exact results you want, pore over the "before" shades on the box labels when shopping—and make sure your starter color is a match.
Step 1: Don't wash hair for two days before you dye—you want your scalp's natural oils to act as a barrier against irritation, says celebrity colorist Kiyah Wright. If you have supersensitive skin, add a packet of Sweet'N Low to the dye to help stop the drying effects of ammonia.
Step 2: Do a strand test first by applying color on a small section. This will help you work out timing. Your hair texture will factor in here: The finer it is, the faster it'll lighten—you may need five to 10 minutes less than the box says; if you have coarse or dry hair, you can go by the recommended time.
Step 3: Read, reread, and follow the box instructions to a T. (Exception: Don't apply color from roots to ends in one go; see step 4.)
Step 4: This tip helps get even color every time when you're dyeing your whole head: First, apply dye a half-inch away from your scalp and work toward ends (the heat from your head makes the color develop faster at the root). Then, halfway through the processing time, go back and cover your roots. When applying the dye, use a color brush to get more professional, precise results.