Ken, I don't know if this helps or not but here is his listing from Booth's Record. Would the fact that he was "Apptd Regt. Sergt. Major" give a clue as to his being the regt. color bearer? What about the date of the appointment. Perhaps somebody can tell us when the regt. was transferred to Confederate service.

Richardson, W. G., Pvt. Sergt. Major Co. F, 16th La. Inf. En. Sept. 29, 1861, Camp Moore, La.
Rolls Oct. 31, 1861, to Feb., 1862, Present, Apptd. Regtl. Sergt. Major, Oct. 10, 1861.