Trouble changing background colors – On Assignment (Modularity) Theme

I am developing a new site at https://fiveleavesleft.jasonparkerquartet.com/ and want to change the background on the main page to black (all the white parts).

There is an option to change the page background to black, but that changes ALL pages, and I only want to change the landing page, not pages and posts.

Any help is greatly appreciated!

Jason Parker
https://oneworkingmusician.com