Heres a script to change the background colour of your site:

<form name="BackgroundColor"
method="post">
<input type="button"
OnClick="document.bgColor='HEX CODE';
"value="TEXT HERE">
<input type="button"
OnClick="document.bgColor='HEX CODE';
"value="TEXT HERE">
<input type="button"
OnClick="document.bgColor='HEX CODE';
"value="TEXT HERE"></form>