Bazaar beauty editor Jenna Rosenstein wears her hair in a deep, cool brown shade, sort of like Dakota Johnson's, but every few weeks, it starts to turn red. Recognizing that this is a very common state of affairs for those of us who color our hair, she did a deep dive into the science behind it, which you can find at the link below. Come for the color theory; stay for the list of helpful products at the end.
—Izzy Grinspan, digital director
