Change background color of iframe issue

JavaScript is what you need. If you are loading iframe when loading the page, insert the test for iframe using the onload event. If iframe is inserted in realtime, then create a callback function on insertion and hook in whatever action you need to take :)

An <iframe> background can be changed like this:

<iframe allowtransparency="true" style="background: #FFFFFF;" 
    src="http://zingaya.com/widget/9d043c064dc241068881f045f9d8c151" 
    frameborder="0" height="184" width="100%">
</iframe>

I don't think it's possible to change the background of the page that you have loaded in the iframe.