One of the oddities of the A3D configuration is the change to, but apparently not a retrofit of, the fuselage fuel system vent.
It was originally a very small vent mast on the lower side of the left horizontal stabilizer.
Even after the bottom half of it was painted red, it's not very noticeable:
For some reason, on all A3Ds starting with Bureau Number 142650 and subsequent, both Bombers and Versions, the fuel vent was changed to a large mast extending from the left side of the aft fuselage. (The small red tube below the fuel vent mast was added at the same time; it was a drain for the vent system.)
The change coincides with the introduction of the tanker kit in production. It must not have been changed for a particularly important reason, since it doesn't seem to have been retrofitted to A3Ds before BuNo 142650, even on Skywarriors that have the tanker kit installed.
In 1956, at age 12, I lived on NAS Sangley Point in the Philippine Islands. Always enamored with airplanes, I imprinted on the Cougars, Banshees, and Skyraiders then being deployed. Not able to be a Naval Aviator because I was nearsighted, I instead became an aeronautical engineer and general aviation pilot. Now retired, I write books and monographs on U.S. Navy aircraft.