For any of you who want to change the colour of a single page only, try this:
/*change background colour of single page (outer frame)*/
body.page-id-#### {
background-color: #ffffff;
}
/*change background colour of single page (article on a single page)*/
.single.separate-containers .inside-article, .page-id-#### .inside-article {
background-color: #ffffff;
}