Spoiler
Perhaps a Union regiment that wears the coats as seen in the movie Gods and Generals. 
That was the 69th New York. Are you talking about the part where the Union army attacks Fredericksburg?
The attack on Mayre's Heights aye by the various brigades. I believe if i'm not mistaken it was the 28th Massachusets but i don't know too much about it.
No, I'm telling you it was the 69th New York, because it was. There was a caption as they were marching through the dead body filled streets. "69th New York Volunteers, Irish Brigade"
You're correct but also mistaken. The 69th New York participated aswell as the other regiments in the Irish Brigade. Just scanend through the scene in the film again but cannot find a caption of that sort.
In the movie, the regiment that the camera is closest to is the 28th Mass. They were the only ones with a green flag that day and you can clearly see the flag in the movie. However, St Claire Mulholland was the col of the 116th PA. So the movie is "interesting" in the fact that they have the col of the 116th PA leading the entire brigade while in front of the 28th Mass. In reality, it was his(and the 116th) first battle, the 116th was all the way on the left flank which is where he most likely was, and General Meagher led the brigade for most of the charge until he went back to get his horse.
The brigade's battle line from left to right was: 116thPA, 63rdNY, 28MA, 88NY. 69NY
The 28th was in the center because they had the only green flag.
