I'll offer a thought.
The color of the target would depend on the location of the switch stand. In other words what track and what track leading off it. Somewhere there would be a standard plan indicating placement of target colors.
I have been scrutinizing this view and there are a couple items of note.
Preparations for standard gauging are under way. Standard gauge ties are in place and rail for standard gauge along side the track.
Placement of standard gauge ties on the main line (the track Jackson's train is on) has not been completed.
Down the track, the other switch is lined for the passing track. I do not see that a target is in place on that switch stand. It would appear that the main line is out of service.
Zooming in on the track ahead of the train, near the mining structure, there appears to be a large pile of rocks on the track. The man pointing is indicating where the rocks came from.
At least this is my interpretation.
Jimmy