You would create multiple stylesheets with different color combinations (and background images) and provide the selection somewhere on the screen. On clicking, you would switch up the stylesheets and write the information on which stylesheet the user wants in a cookie. The latter, being the core operations within this script, cannot be done via html, so you will need to resort to either:
a) client side scripting, like javascript (forum216) or
b) server side scripting, like php, asp, coldfusion, perl -- whatever you have available.
You should ask your question in those forums then.