Did you try the "Classic" Theme?
Also, you can change the color of the Body in layout mode by clicking the "Body" title and changing the Fill Color in the Inspector's Appearance tab.
I looked at the classic theme, but until you recommended it, I did not realize that the background is white! Thank you.
The key to your second suggestion is to click the Body Title, otherwise you cannot modify the background colour.
Two learnings today! Thank you for your suggtestion.