Brett on 08 Oct, 2017 05:22 PM
Note that it is possible to modify things like that using the Additional CSS under Style preferences. You can add override styles there that apply to all themes. All themes also get a body class based on their filename, so you can modify just Upstanding styles with:
Brett on 08 Oct, 2017 05:23 PM
The classes are auto-assigned, I didn't double check that one. If you right click on the preview window and Inspect element, you can see the actual classes on the body tag (and even experiment with style changes live in the preview).