"When natural hair pigments are touched with ammonia or peroxide solutions, they oxidize and turn warm. When the deposited pigment starts to fade, that oxidized color is exposed."

The solution is reinfusing the pigment with products like Matrix Shade Memory - also featured.

Thia leaves Elle readers with this helpful tip in determining if they are considered cool or warm toned. Head to a fabric store, buy a swatch of metallic gold and one in silver (which reflect, respectively, warm and cool light). Pull hair back and frame your face with each piece. "The wrong color will make skin look blotchy and undereye circles and lines around the mouth more apparent. On the other hand, the right tone makes skin creamy and smooth."

More than 3 Million readers will see Matrix Shade Memory along with Thia's tips in the December issue of Elle available on newsstands now.