I'd love to do this, too.
After looking into the code a bit, I found that the background colour applies to the view itself (when you click "View larger version", you'll see the name of the view on top, and behind that is the view's background colour), but that background isn't part of the section of the view that's getting embedded.
The part of the view that's getting embedded has a background that you can't change- it would have to be changed on Airtable's end, and since there's no option on that end for us to customize embeds, what we get is what we get. That said, if they were to make it so that the part we're embedding has a transparent background.
For any Airtable support people who might see this: if you make it so the CSS for the div with the role of "region" has the same background colour as the one set in the view's link, that'll do the trick (aka the CSS selector that points to exactly the div you need, and only applies when the view is embedded is: ".embedded [role=region]"). Yes, there's more than one div with that role, but this change will only show up in the one that's the child of the div with the id that says what the view type is (ex. #galleryView)
