The only CSS styles bound on moible there are .bx-media-phone .bx-layout-col. But the main part which is responsible for it depends for the CSS classes like bx-layout-bcb-bar1 (or bar2) bx-layout-column-thin and bx-layout-bcb-content bx-layout-column-half.

But in your case you may add the RAW block with Javascript which will change the order of the bx-layout-col divs.