[Erwin]

Go to your Admin Control Panel:

www.yourforums.com/admin/

(change the domain name to your own)

Under the header Syle, click on Modify. Then click on fonts/color/etc next to Default.

And change your colors.

To change the layout, you need to change templates. Under the Template heading, click on Modify. Next to Default, click on Show All. These are all the templates you can modify. To change the forum homepage, modify forumhome. To change the list of threads in a forum, modify forumdisplay. To change how the thread page looks, it's showthread. To change how posts look, it's the postbit.

Hope that gets you started.