Hump signeal color order

I have almost completed restoring a Guilford hump yard signal from Mechanicville NY. However, I am not sure how the bottom two lights are arranged.
I know what the signals meant and I also know the top two signals are in the right order
"Green light indicates fast speed ahead.
Two yellow lights indicate medium speed ahead.
One yellow light indicates slow speed ahead.
Yellowabove the red indicates back up.
Red light indicates stop."


Since there is a yellow over red I assume that the second yellow light is above the red light however you could have them flipped around so the red is on top and for yellow over red the top yellow is lit, also what one of the yellows would be lit for a single yellow?

Just guessing, but I recall seeing ETT instructions about foggy conditions at the Mechanicville hump, so I'm thinking that the arrangement is correct and the upper yellow and red would be the ones lit for reverse moves, there being sufficient distance between the two lenses to reduce potential confusion during fog.

From p. 119, "BOSTON AND MAINE RAILROAD TIME TABLE NO. 28," (yes, all caps and timetable as two words) effective Sept. 24 1939:

"In the use of day-light hump signals at Mechanicville receiving yard, the following indications will govern:
Green light indicates fast speed ahead.
Two yellow lights indicate medium speed ahead.
One yellow light indicates slow speed ahead.
Yellow above the red indicates back up.
Red light indicates stop."

There were also fog signals transmitted by horn blasts. Given that there were also steam and smoke back then and sometimes two switchers working the hump, there must have been more than a little anxiety during poor visibility conditions.