Page content BG color and Search Topics?

I want to change the background color on the main pages of the Pinboard theme. I have a child theme set up and can’t find the code as to where I’d do that.
I got it to work on the home page,

#container {
background: #5f3819; */works on homepage*/
}

ALSO, this is my first post in this support forum and I don’t see a place to ‘search’ for a topic. Am I missing something? Or do we just have to flip through all the posts to see if we can find something related to our questions?

Thanks