From : HERE

We will not likely update the default editor to support these options. Our goal is to keep the UI as simple as possible and guide users towards standards like CSS. Things get messy really quickly when you start setting font sizes and colors via a toolbar.

Having said that, it is really easy to change your site to use a more full featured toolbar.

Using a text editor (like notepad) find the file /graffiti-admin/posts/write/default.aspx and find the element called <GlowEditor:Editor and change the attribute toolbarset from simple to “default”.

Thanks,
Scott