I want to customize the Bootstrap theme in my application so I created this file: src/bootstrap.scss and updated the styles value in the angular.json file like this "styles": ["src/styles.scss", "src/bootstrap.scss"]. The bootstrap.scss file have the following content: // Import Bootstrap's functions and variables @import "~bootstrap/scss/functions"; @import "~bootstrap/scss/variables"; // Override Bootstrap variables $primary: #ff5733; // Change primary color $secondary: #33c1ff; // Change secondary color // Import Bootstrap styles @import "~bootstrap/scss/bootstrap"; When I do ng serve, I always get the following error: ✘ [ERROR] Can't find stylesheet to import. ╷ 2 │ @import "~bootstrap/scss/functions"; │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ╵ src/bootstrap.scss 2:9 root stylesheet [plugin angular-sass] angular:styles/global:styles:2:8: 2 │ @import 'src/bootstrap.scss'; ╵ ~~~~~~~~~~~~~~~~~~~~ Why? I properly installed bootstrap and ng-bootstrap. Continue reading...