Page Backgrounds Issue

Hello there,

I need to set the background color of following page to #F2F1F2. The page is is post=15, but I couldn’t be able to find the correct css seperator each time.
For example,
.body.page.post-id:15 {
backgorund-color: #F2F1F2;
}
something like this doesn’t work. Could someone please explain that how could I change the background color of each page individually and how could I find the correct seperator inside the dev tools for situations like this? Thank you very much 🙂

The page I need help with: [log in to see the link]