> I set bg=dark in my ~/.vimrc file and everything is fine. The problem is 
> that when I run "su -" and then run "vi" on a file I'm back to dark blue 
> text on a black background. I looked for a global .vimrc file but can't 
> find one. Any pointers?

Yeah, the global one is not a .vimrc, but vimrc.  On my Gentoo box it can be 
found in /usr/share/vim/vim62/