Just got to thinking. What configuration are you using for the access panel on the belly, just forward of the tail hook pivots? The reason I ask is that ALL of the -6s had a bulged radome on the bottom of the panel for a doppler radar antenna prior to the change in paint schemes. When the A-6Es were updated and third generation of Prowlers came on line, starting in the 1986-1988 time frame, that radome and the doppler system were removed. The panel was completely reskinned using a single piece of aluminum when the electronics were upgraded at NARF. That being said, any EA with the booms on the front of the outboard wing stations should have the doppler radome while those without the booms can go either way.
BTW, is this the paint job you were referring to:
I know it's not the whole plane but I thought it showed enough. That paint job was of a prototype updated A-6F that wasn't built, hence the non-grey paint job. One thing this shot does show that was legit for operational aircraft is the yellow on the leading edge. This was a clear tape that was used to protect the leading edge paint that, over time, would yellow. It was very obvious on the grey/white aircraft, as can be seen, not so much on the three tone grey.
Grumman was known for painting prototypes in the white and blue scheme. If you watch this video of the X-29, you will find it's got the same basic paint job: