Remove white space / margin / padding around content in middle column

I am using the Hueman Theme, and it’s awesome! However, I would like to remove all of the white space (padding? margin?) around the content in the center column. I am currently using the 3-column layout with main content in the center, and I would like my sliders, etc. to extend all the way to the gray background of the sidebars. Is there a way to do this? I already tried changing both the specific row’s settings and the global settings to “full width” but to no avail.

My site is https://trisef.com