I have selected a background image for a section to be used on desktop. When switching to mobile I can use a different background image all right, but I can’t remove the background image and instead use a color for the background
that’s true. Background image control will have a priority over background color. What you can do is to add the following CSS to the breakpoint where you want to remove the background image. It will unset the css style.
%root%{
background-image:unset;
}
Or you can choose one transparent image, that will also work.