You still don’t edit the html. You have these options: 1) Add new class for just that page, 2) great a different external stylesheet and link it after the global one, overriding its styles for the ones you want, 3) overriding the global stylesheet for those classes with inline styles in the header block of the page, so the content doesn’t have to be changed in any way.
Oh, there’s one more way - you could have a javascript function dynamically change classes based on page numbers using the DOM. Many ways to solve the problem.
Well, all you have to do is treat that element as an exception to your formatting and override the standard style sheet with an inline style.
You can’t really blame this on CSS. Consistent formatting across all your pages is one of its main benefits, and now you are deliberately breaking that consistency. This is like having to bold or italicize certain words in a sentence but not others – there’s nothing any language can do about that, because in the end that particular element (or word) is simply different from all the others and you have to mark it as such one way or another.