Hi Jesse,
Thanks for posting this on the forum. I think I found a solution to your issue of the white background showing between pages. You can create a Master that is layered below everything else, and just has a shape that is the color that you want. The Masters don't disappear between pages, so if you have a grey (or whatever color) shape on your Master, that should do it.
To make it easy, you can create your new Master, add your shape, and then right click on the Master and choose "Apply to all pages > on Bottom" (see attached image).
You'll still see a white background while the lesson is loading initially, but not between page changes.
Hope that helps!