They would like to have the two sidebars displayed in reverse order when viewing the site on a mobile device. So, that the secondary sidebar would display first under the content, then the primary sidebar.
Perusing the theme’s layout files, I am not seeing where the call is to make the changes myself.
Thanks to the theme’s advanced layout options, the sidebars functionality is buried pretty deep in the code.
You can find the tempera_get_sidebar() function in includes/theme-functions.php.