We need to go back and look up thread (or previous thread) for the post, but one of our military people gave us an insight into the Red/Green Castle thing. Perhaps someone else out there can help with the appropriate attribution and can verify my memory:
I understood one meaning can be that the Red Castle = air to air battle
Green Castle = land to air battle
I don’t know if the “land” can mean “fixed.” In other words, I don’t know if Green applies as land to air only or if it can also apply as ship to air.
The 'Flag' exercises are aviation related. These are held at the the Nellis AFB range complex so it would be tough to get any ship there.
Not being an AF puke I think their air to ship stuff would occur during their PACAF (Pacific Command Air Force ) exercises with the squids.