Change background color for all pages
You can change the default page background color for Normal Pages from Theme options > Pages:
You can also change the background color for Blog, Portfolio and Shop pages the same way from the Theme options (Theme Options > Blog, Portfolio or Shop > General > Background color).
Note: if the background in the page is not changing, please make sure in the page builder you’re using that the sections in the page don’t have already a background color.
Change background color in a specific page
If you want to change the background color of a specific page you can do that by changing the background color of the sections of that page directly from the page builder you’re using (WPBakery or elementor).