All hair dyes fade, whether permanent or not. The culprits are oxidation (unavoidable) and the sun, so your first line of defense is to cover up. (Products that contain sunscreen can help a bit, but they're not enough.) Use a gentle shampoo, then condition as much as possible -- permanent and some semipermanent dyes cause at least a little cuticle damage, and some cause a lot. If you've colored your hair so much that it's seriously damaged, see the section on damaged hair. Between colorings, shampoos that contain a colorant can help freshen up your look.