Change the page background colour by pasting CSS:

<style type="text/css">

body.allow-sidebar #main { background: #CC9999; }

</style>

 in:

 Site > Page Code Injection > Head Area [Bottom Box]

One way to find Hex code of the colour is to use the colour palette and select the Web Safe Colors from the Format > Show Colors

See the example page here: [mp3] Oh, I don't know