fspring widgets color change

I am trying to change the color on both the left and right side of the page (the blank portions of the screen) to be color #564226.

I’ve looked in the stylesheet file and cannot see where I can change this color. I’ve been able to change several other elements on the page, but this has proved more difficult.

https://www.littlemonkeybutt.com/

I apologize up front, I’m a noob and don’t know CSS. I’ve tried looking in the help files but have been unsuccessful. Appreciate any help you can provide.