> As a kid who was very curious, I noticed signals were always lit GREEN. I seem to remember this clearly for many years, they were GREEN whether there was a train in the vicinity or not. (of course, they would turn red if needed).

This is called "normal-clear ABS", with the signals always illuminated. The Santa Fe used this method because most of it's sidings were equipped with spring switches, and this enabled a train in the siding to observe and comply with indications of the signal on the main track for opposing trains.

> Then suddenly, around the mid 1980s, they all went dark. And they would only turn green when a train was approaching (or red if one was coming).

This is called "approach lighting", in which the signal lights up only when the block in front of it is occupied. The change was probably the result of the FRA's insistence at the time that all tracks connected to the main track have a separate signal governing movements which were entering the main track.

> My life long answer I’d like to know was there ever a time that signals were always turned on green at all times?

Yes, before the 1980s change. However, whenever there was a train approaching a signal, the signal governing in the opposite direction would be red.