all you need to do is use css inserts (ATO->Add HMTL/CSS Inserts->CSS Insert) like this
HTML Code:
div.category-red-wine {background: #red;}
div.category-books {background: #blue;}
div.category-white-wine {background: #yellow;}
the name will be 'category-' plus teh category slug (dashboard->Posts->Categories)
the last insert will take prescidence, so if you had a post with the category 'books' and 'white wine' then it would be YELLOW. If you had the CSS in this order
HTML Code:
div.category-red-wine {background: #red;}
div.category-white-wine {background: #yellow;}
div.category-books {background: #blue;}
then the post would be BLUE