Force Cache Clear of CSS

I’m having some issues with my app in that I make changes to the boostrap-variables.import.less that are not subsequently rendered into the served CSS but the old value remains.

How can I force the css to be updated? I cannot find the files anywhere locally on my machine to modify because they are generated at runtime right?

Thanks for any help on this

I ended up just forcing a overwriting class to fix this. Seems the less variables can get stuck on values… did not find a fix.