Using less will allow you to easily modify the core styles of the framework with a simple line, no need to search and replace in all the css code. In this visual guide you can see all the variables that you can easily change with Less, as well as the default value:
In order to generate the files, I am using lessc compiler, it is the easier way I have found to generating the css from the less files, after looking at some options such as lessphp that I have not been able to make work properly – due to my lack of proficiency, not doubt about that!-.
Good luck if you are in the same mission! and please share with me your doubts and concerns!