I am using Zurb\'s Foundation framework, and I would like to know how I can edit the default values of the SASS variables. I searched all over the internet but I was not able to
jOk, there are global variables you can configure (_settings.scss), there are also default (!default) variables at a module level, you can find documentation of in the online docs, i.e. for buttons http://foundation.zurb.com/docs/components/buttons.html (scroll to bottom).
Because these variables are assigned with SASS's !default it is possible to override this in the global scope, but you must make the new variables available before the styles are declared. As in, the variables must appear in the cascade before the buttons do.