If I understand what Lee is describing, it will leave the green light on permanently.
There is a simple way to operate a signal from a control rail (an insulated outside rail), which I have described a number of times on the forum, using only an extra incandescent lamp:
Connect the green lamp's terminal to the layout common, that is, the outside rails generally. Connect the red lamp's terminal to the supply, whether the center rail or a separate accessory supply. Connect the signal's common (the terminal connected to both lamps) to the control rail. Then connect an extra lamp in parallel with the red lamp, that is, effectively between the supply and the control rail. The extra lamp should have the same voltage rating as the signal lamps but draw twice the current. When the signal lamps are number 52s or 53s, as they often are or could be, a number 57 is ideal as the extra lamp. An alternative is to use two extra lamps in parallel, of the same type as in the signal.
A couple of years ago, I was surprised to come across almost the same idea in an old book I was reading. [Raymond F. Yates, Making and Operating Model Railroads, D. Appleton-Century, New York, 1943] It was attributed to Albert C. Kalmbach, the founder of the very company that sponsors this web site. The difference was that he used an ordinary resistor in place of the extra lamp. However, lamps work much better in this circuit.