It is quite clear Dooku never understood the brutal truth; treachery is the way of the Sith. \n ""> Several Sith Lords in Star Wars canon can be identified by their trademark yellow eyes ...

Count Dooku never got to be a Sith master, as Palpatine had Anakin decapitate ... Via its glowing red eyes, it drew potential victims in and then, once they put the helmet on, possessed them.