Configuring how posts are displayed in admin panel

Hello!
Does anybody know how to change the way posts are siplayed for the user in the admin panel? When I, for example, choose the “H1” formatting tag, it shows up as “Georgia” when, in fact I want it to be displayed with my them style and “Lucida grande”, 16pt.

How do you do this? Can I configure it by making a plugin, or is it more simple?

Thanks!
Michael