Zone 1 is the root/root shadow area. "This is generally the first 1/2 inch to 1-1/2 inches of the hair," she explains of the regrowth area. This is where she starts to shadow root or blend to cover up any foil lines from highlighting. "This is the darkest area of the show root," she says.
Zone 2 is the transition zone, or the mid-lengths area from where Zone 1 ends to where Zone 3 begins. "When doing a shadow root, this is the area where the shadow root begins to lighten and soften, and creates the transition from dark to lighter," Tyrrell says.
Finally, Zone 3 is the ends of the hair, which she says are typically more porous, "therefore I will generally color this section of hair last so the color doesn't grab and darken," she explains. "This area is always the lightest section when creating a shadow root and creates the bright pop on the ends."
In this example, Tyrrell used two different toning formulas. The first was applied to the shadow root in Zone 1 for 10 minutes, then pulled through Zone 2, and she used a second formula that was applied to the ends.