One of the big changes in Bootstrap 3 was the removal of a lot of the visual styles. The styles were removed as Bootstrap is designed to be a framework to build upon, and not just be left with the default look.
However, these aren't gone for good and have been moved out to a separate file, which is included in the source. The
theme.less file brings back the gradients from Bootstrap 2; we just need to import it to our main
bootstrap.less and add the following to the bottom of the file to include the theme:
For an example of what the Bootstrap theme does, check out getbootstrap.com/examples/theme.