By Erica Metzger
When fair hair becomes blah, it's usually because you've got mineral buildup. "Blond and highlighted hair is porous so when it absorbs rust or chlorine from your shower water, it gets a dingy or muddy look," explains Stephanie Brown, senior colorist at the Nunzio Saviano Salon, in New York City. A clarifying shampoo once a week helps. You may also want to buy a new showerhead that has a better filtration system.