I saw the green flag in the movie, Gods and Generals on cable TV, was this flag based upon the flag in 1847?

Question

I saw the flag in the movie, and it look similar to the Saint Battalion flag that the regiment had during the US Mexican War 1846-1848.

Answer 1

It was the Iris flag.
the Irish soldiers in the Union ranks consistently distinguished themselves in
battle. The famed Irish Brigade was organized and led by General Thomas Francis
Meagher, an Irish revolutionary who had come to the United States after escaping
imprisonment in Ireland for his role in the disastrous Young Ireland Rebellion of 1848.
The Brigade was made up of the 63rd, 69th and 88th New York Infantries, the 28th
Massachusetts Infantry and 116th Pennsylvania Infantry; they marched into battle under an
emerald green flag with a large golden harp in its center.

Answer 2

Blah got it!