How to add background color/image for a specific page only.
1. From the WordPress left menu, go to Pages and open a page to edit.
2. Scroll down to Post Options section and click on the Main tab.
Note: If you don’t see Post Options section in the page editor, you need activate the plugin Advanced Custom Fields PRO via Jupiter X > Control Panel > Plugins.
3. Set the background settings in the Styles section.
4. Update the page to save the settings.