I have one master page that is used for three pages. Thats how its going to be I cant do anything about it. This master page generate a class element that have a background color of white. I want to have it white on one of the pages and black on another. 

But the problem is that both pages use same master page which means I cant specify to have different color. The pages are generated by a hive which means that I cant edit the pages. I can only use the css file and the master page.

Any kind of help is very appreciated