Ken called me about this and I pulled my file for color guard of this regiment.
Wally Cross' book on the 14th states - "The Fourteenth Tennessee Regiment lost three color bearers before the crest of the stone fence was reached. The names...Thomas Davidson, Company A, Columbus Horn, Company G, and Powell, a black corporal of Company C." (Page 72)
Dr. Michael Bradley, a well known Tennessee historian and professor, emailed some friends in 1997 about the black member of the color guard and that states - "The man was George Johnson, 14th Tennessee Infantry..."
I have copies of Ken's files for this regiment and the color guard and he has type-written pages. Sgt. Thomas Mockbee's account of the battle states - "Gettysburg - Three men being shot down with the colors of the 14th before the crest of the stone fence...Thomas Davidson, Columbus Horn,...Powell, who fell apparently dead just after crossing the Emmitsburg Pike, and within 100 yards of the fence it was carried by Barney Smith (Co. F)." Ken in his notation next to Powell has (negro?).
On a second sheet of two pages that Ken also typed up is this - "George Johnson, color bearer, Free person of color - no CSR found."
So it seems that Mike Bradley's email is the source of this black color guard member.