I take it your using an iFrame to load the content onto your website!? Could you provide a link to what page your using your hosts stats on so I can see what you're seeing. Backgrounds within the iFrame take their color from the HTML document they are loaded from. Because of this your going to find the background color of your parent page, and copy it to your hosts css file. If your not sure you have the right color, you can use Google Tools. Right Click on the iFrame from your website, and then go to inspect element. From there you can edit the CSS on the fly until you find the right color, from there copy to your css file and upload here again.