Trouble Changing Background Color of one page for Tremont template

I feel like i've exhausted my CSS knowledge here. I've been attempting to change the background of just this one page on my site. I'm running 7.0 Tremont template. Also, on a business plan.

https://www.johnpauljay.com/publicis-performance

@johnpauljay this should work

#collection-657365d03fbc7c16be3fe7a9 {
  #mainContent {
    background: #000;//change me to your color     
  }
}

This worked, but I would like to keep the header & footer portion of the page white. Also, make the text on just this one page white.