Here are three men of the regiment with similar names, however, their CSMRs do not list duty as Color Bearer.
Patrick McMahon
Patrick Meagher Sgt Co. A & F
Patrick Moriarty
Patrick Marr Sgt. Colorbearer 1st Mo. Inf. Regt
Capt. Joseph Boyce's Memoir Sept. 1, 1861 Co. D