I think the main issue for your original question was that our forum software doesn't default to saving a copy of our sent messages. I feel this isn't a good default & many people will only find out after they've been using the site (and have sent many messages) for a while.
Birna, do you know if this can be changed?
Meanwhile RobOK, the look & feel, sidebars etc can be individually tweaked.
But in my case, it was recommended I change to a particular "theme" in the hope that it would resolve a different technical issue. In doing so, i acquired the yellow feel, plus various other changes like some sidebars.