For the theme that would require editing the template files and the CCS files.
The main header and footer are stored in templates/default folder.
They are called global_heaer.htm and global_footer.htm and they can be edited in a text or html editor.
The CSS is stored in the templates/default/css/
Eventually longer term I would like to either figure a way to intergrate with some of the forum systems and use their style information directly for the colors/theme.