Content Builder is a WordPress Plugin which lets you feel free to create any page layout that you can imagine, and it is simple as drag & drop. Plugin will improve your website functionality and save your time with content managing.
Bootstrap framework is used for theme and backend. If you wish to change colors, font's and other css setting's you need to edit: content-builder/theme/theme.css all changes will be instantly loaded in theme and backend.
Content Builder frontend & backend is designed width Object Oriented technique. So it is easy to edit and extend plugin with your own widgets