TheMAG is built with SCSS and use the Gulp task runner to do all things you need to compile/recompile the theme styles. With this setup, you can easily override theme colors, components, etc.
yarn installfrom the sub-theme directory:
gulpcommand to watch for changes in the _src/scss directory and to compile SCSS files.
If you override the entire theme style, it is a good idea to override
themag/global-styling library to prevent CSS duplication. To do that, in the subtheme *.info.yml file (themag_st.info.yml) uncomment the following lines:
libraries-override: themag/global-styling: css: theme: assets/css/themag.css: false