The orange and gray goes back at least to the mid-1950's on locomotives. And I remember the fronts of the old MP-54's being bright orange in the early 1960's before the Worlds' Fair.
Orange and gray, in some style or another, goes back to 1950, as the elegant but impractical Tichy scheme was introduced on FM C-Liners. The simplified gray/orange came around 1955, as ALCO RS3's replaced the last of steam. The World's Fair "swoop" was a cleaver reintroduction of the dark gray scheme, and lasted until around 1968, when the pastel "blue-birds" (L2's) came on line. The pastels went out in favor of darker blues, and the rest of the fleet started getting the blue/yellow "M" scheme. Thank God in heaven, I didn't have to see the desecration of the fleet in Milwaukee Road blue/white waves.
That being said, The heritage colors could be introduced on individual units today, and using some clever thinking and some printing, an excellent history program could be launched. Will it happen? NAW! Should it happen? YES! MTA officials have only to contact me for consultation.