From this site http://www.pets-opedia.com/cats/cthcec11.htmlLice are about half the size of fleas: 1mm (1/32 inch) which can be seen by the naked eye. They are yellowish/white in color and stick to the cat's hair. Cat lice cannot affect humans, and Human lice cannot affect cats.
Lice can cause anemia, itching, appetite loss, temperament changes and general discomfort in your cat. There are several shampoo's and sprays that you can use to kill the lice. Contact a veterinarian for special prescriptions and additional instructions they may have.