How to have different layout backgrounds on different devices?

Select a layout you want to adjust.
Select layout colour by clicking Background in right toolbar.
Select layout colour or image/video for the background.
Select "Visibility" in the right toolbar.
Select devices that you want your layout to appear in (e.g., a wide screen, desktop, and tablet).
Select a different size of screen above your website content (e.g., phone).
Insert another layout in the same position where the previous was.
Select that layout and choose layout colour by clicking "Background" in right toolbar.
Select different layout colour or image/video for the background.
Select "Visibility" in right toolbar and set it to show for that layout only (e.g., phone).