Train Order signals

Anyone know why the NYC used search light signals on there towers for train orders? What color combinations did they show. Thanks

The searchlight heads replaced semaphore blades on train order signals/Manual Block signals.
Where there was dual usage,there were 2 plates installed on the mast,White letters on a black bachground,
one plate had the letters TO , the other plate had the letters MB .

On the mast it would look like this:
TO
MB
Colors red,yellow,green used
On towers a head with the Lunar White color was used.

The TO color light signal on towers was amber, not lunar white.