I managed this by giving the body an ID (page name such as home, contact-us etc.). Then in my nav I gave the "a href" a class which matched the body ID.
My CSS then looked like this:-
Code:
#home .home, #contact-us .contact-us {
background-color: #000;
background-repeat: no-repeat;
background-position: left top;
}
The only thing you need to change on a page by page basis is the Body ID as all your nav links are classed up. I also run multiple stylesheets and it's no problem.