From LQWiki

It is possible to theme OpenOffice to look exactly how you, the user, wants. Ximian has created a lovely looking version more in keeping with the look of the Gnome desktop manager. It is possible to bring this to your current OpenOffice installation as detailed by pcc-services

1. Download this file: http://www.pcc-services.com/files/oootheme.zip
2. Create "soffice.cfg" directory under ~/.Openoffice.org/user/config (~ meaning user home e.g. /home/foo)
3. Decompress zip file to this folder.

Now restart OpenOffice (quickstart should be disabled) and you will have a gorgeous new OpenOffice. This theme can be customised, by downloading another tarball from pcc-services and following the included instructions.

This will also work under a Windows installation, but create soffice.cfg under C:\Program Files\OpenOffice.org1.1\user\config (presuming accepted default installation path, and version 1.1). This means you can have a consistent look if you have a dual-boot machine.

for OOo version 1.1.1 in linux the directory is like: file:/usr/local/OpenOffice.org1.1.1/user/config/soffice.cfg depending on where you have it installed