Change post background color

I was trying to change the background color of a post.

I tried this code on my page https://gettysburgconnection.org/support-our-businesses-february-is-i-love-local-month-in-adams-county/

body.page-id-50184 {
background-color: #FAE0FD;
}

I see the code on the page but the background color hasn’t changed.

Thanks.