There are better ways to green light shooter(s) than taking out a Billboard. Which brings to mind why RED would be used as a Green Light/Go signal?
JFK knew that the RED RINGS on the beach at BOP were there to identify the location of the Cuban in Brigade 2508, and a signal to the air cover that the CIA had promised the Cubans. The RED RINGS served a dual purpose.... A) An instant visual reminder to JFK that he had caused the brigade's capture and the deaths of dozens of the "Freedom Fighters"...... That's what the CIA wanted.... And they also notified LBJ, that the trap was set.... It required only his signal to spring it.