@sankum i do not know, but you can use the developers window elements tab to discover and test css changes
see the second link in my signature below for a starter discussion on how to use it
you can also discover some info from the css we provide in the module folder
MagicMirror/modules/default/weather
weather also uses the nunjucks template formatting file,
.njk, it is a text file, you can see the class assignments there too