@NYC Fan posted:Oh...I thought it was right around 1937 that the rules did away with the requirement of class lights on the NYC mainlines.
The "rules" did not do away with class lights at any time. They were specified in the 1956 rule book, which was still in effect at the demise of the NYC. By 1961, or earlier, there were special instructions in the timetables of most districts stating that the display of white signals should be omitted. That was not true of green signals. We didn't run many second sections of scheduled trains, but the rule was in effect.