From the theming movie on youtube I learned that the "classes" box can be used to add css to the article, page etc.

I have been trying to change the appearance of a page for example by adding there: background-color.

the background color is defined in the css variables.less

unfortunately this does exactly nothing.

could someone explain how to use this classes box? i am trying some stuff with the standard vanilla theme.

or to put it another way: which classes from the vanilla theme can I put in the classes box?