Press alt+k and look in the representation of the list box, you should see what he means by "Gray[ed] text".
rela: Add someone to your notify list who isn't online, open the notify list window (with the button on the right hand side of the toolbar, not the address book), right click and choose "Show All".
Offline nicks appear in the "Gray[ed] text" colour, and server names in the "Title text" color.
