remove border of grid layout for posts and grey gradient

Hi,
Thanx for the nice theme!
I’ve tried to remove the light grey borders around the grid layout for posts om the home page, but I cant find a way. Can anyone help me? I was able to remove the shadows by simply unchecking the box “Apply a shadow to each grid items” at the Post List Design. But I can’t find anything there. css doesn’t work either…

I also would like to remove the grey gradient in the grid layout for posts. Any ideas?
Thanx