Changing footer background color

Hi! I love this theme and think it is perfect for what I’m looking for: typography centered, no frills. So, before anything else, thank you very much for taking the time to create it.

I tried to use the FSE feature to change only the background color of the footer, but I couldn’t do it because it changes the background of all the other sections. Is there a way I could change only the footer background? Also, I’d like to add a border to its top.

Any advice would be much appreciated. Thanks in advance!