Some fans believe Palpatine was using Force enhancement to cover up his Sith disfigurements (due to decades of using the dark-side) and yellow eyes before his fight with Mace Windu.
Is it possible he taught Dooku to do the same? Or is it because Dooku was once a Jedi (and therefore not totally consumed by hate) that he does not look disfigured like other Sith?