Coloring your hair is like doing your taxes—you’ve been doing it forever, and you’re still a little unclear about how it actually works. Well, consider this Hair Color 101. Permanent dye—usually a mix of hydrogen peroxide and ammonia—deposits color into your hair shaft. Bleaching is fancy salon lingo for stripping color out. If you’re choosing between the two, permanent dye tends to be the less-damaging choice. (It can still rough up strands, mind you; ask your colorist about gentler ammonia-free formulas.)

Give your hair (and your wallet) and break between full coloring sessions. Focus first on the roots and try a gloss or toner to revive fading color.

QUIZ: How Healthy is Your Hair?