From the Lester S. Levy Collection of Sheet Music (see link above):
(I have underlined the differences between these lyrics and the ones in the DT.)

JUST SET A LIGHT
Words, Henry V. Neal. Music, Gussie L. Davis. 1896

1. A little child on a sickbed lay, and to death seemed very near,
Her parents' pride and only child of a railroad engineer.
His duty calls him from the one he loved, from this home whose lights were dimmed.
While tears he shed, to his wife he said, "I will leave two lanterns trimmed.

CHORUS: "Just set a light when I pass tonight. Set it where it can be seen.
If our darling's dead, then show the red; if she's better, show the green."

2. In that small house by the railroad side, 'twas the mother's watchful eye
Saw gleam of hope in the feeble smile as the train went rushing by;
Just one short look 'twas his only chance but the signal light was seen;
On the midnight air there arose a pray'r: "Thank the Lord, the light is green."