Changing the background color of all screens
Changing the background color of all screens within a project can be done within 'Themes.'
Once you’re in your chosen theme, choose the ‘Screen color’ beside your theme name.
This will automatically update the background color of your screens.
Changing the background color of a single screen
Alternatively, if you only want to change the background color for a single screen, simply select the screen, and mark the black box beside 'Screen color.' This assures that you overwrite the theme for the specific screen.
Then, choose your desired screen background color.