i am deploying a map (no tiled, no external providers) in a fusion layout.
the map has a background color but this inst recognized by the fusion layout, and shows a silver background.
nonetheless, overview map shows the correct background color.
attached, you can see the main map has no background color, the overview shows the correct background color (the OM ratio is very big, thats why you can only see the background in the overview not the actual carthography)
Yes, the background image (that is also seen in the legend etc) is the default background on the map. I had to hack the image to change the map background because the background colour is hidden behind the image.