...Only the components that get imported into src/styles.scss will be compiled into dist/paper.css. You can also play with original, source files, written in SCSS, in src/. You can customize PaperCSS easily, clone the repo, run npm install and make any changes to .scss files in src/. The main place you might want to make changes would be core/_config.scss, where you can specify new colors or fonts for your CSS build. After you make changes, be sure to build the new CSS files. Do so by running npm run css:build and get them from the dist/ folder.