Have your buttery highlights taken on an orange cast? Don't blame your colorist. "Sun breaks down pigments in the hair," says cosmetic chemist Mort Westman of Oak Brook, Ill. Washing with a purple-tinted shampoo (such as Clairol Professional Shimmer Lights shampoo
, $8; sallybeauty.com
) neutralizes reddish tones, so your hair will look more like Jennifer Aniston'sand less like Carrot Top's.