NS was created in 1982 from the merger of the Norfolk and Western Railway and the Southern Railway Company. They still had individual paint schemes in '89, but they were probably the first of the mega-mergers.
UP? try CSX! the second they got their share of Conrail units they were ALL repainted within the year(possibly the first 6 months)! besides I don't mind seeing the original Santa Fe colors still around, the war bonnet scheme is my personal fave!