Chaning layout

Can someone tell me what the files are to change the layout, Home page, The tabs with Members, Chat, Polls etc etc are, for the love of god I cannot find them so many files. :(

When I mean files for layout, I mean by how to change the color background of the index page, It's white atm but wanting to change a few pages just so many files and have looked in loads of index pages also css files and can't figure out where it is :( Help me please some body.

done.

Instead of saying done, maybe you can show others like yourself what you did so they can use this info for their site as well...Geez i hate it when people don't share.