Yes, it can, but I'm not sure if you really want to. You can configure the appearance of widgets using the options database (that is, under X Windows. I've no idea what the equivalent is under Microsoft Windows). I think Mastering Perl/Tk and/or Learning Perl/Tk discusses this.

I once tried this for a tiny program, just as a proof of concept. It took a lot of hassle but it worked. And I decided to never ever repeat that experience again.