I can’t change the color of the bottom content border. It stays black, because of the css error.
Can you confirm?
Thanks! It should just fallback to “transparent” in that case. We will look into why that’s not the case. It’s possible you’ve deleted a global color used for one of the border edges. If you link the border, then unlink it again it should start working.
Link and unlink does worked 
Ok great! Glad it is working for you now. We should have the underlying issue fixed for the next release.