As Loren notes, the short answer is: FS 34087 Olive Drab with a nose stripe of Insignia Yellow FS 33538.

Starting in 1984, it became Olive Drab FS 34088, due to a change in the FS 595 system itself. Same FS number for the yellow. However, there were thousands (if not tens of thousands) of bombs in the older color still in the inventory, and repainting was glacial speed, with many being expended before repainting happened. So, unless you want to show newly acquired 1984, or post 1984 bombs, it would be perfectly fine to have the older color well past 1984.

Additionally, sometime after the fire on Forrestal (I don't have any exact date to hand) the Navy began to put a protective thermal coating on its bombs. Still colored FS 34087, but the thermally coated bombs now sported two FS 33538 Insignia Yellow nose stripes.

I would highly recommend reading through this discussion:

https://www.britmodeller.com/forums/index.php?/topic/235086999-us-dumb-bomb-colours/

Then, if you want to "wonk out" on the details of Olive Drab, go through this:

https://www.britmodeller.com/forums/index.php?/topic/235128443-so-many-olive-drabs/

A-6 was the Intruder (but I knew what you meant.)

HTH