I was playing road of the dead 2 today to get the insane quest and the first zombie that got on my car had a green hat. I checked the date and today is St. Patricks day...
Most likely an easter egg. Only the developers have control over the games they create and the stuff they put in it. The AG staff don't really have access to the files for the game and even if they did, they'll have no idea how to make it work (I think).
Remember the (literal) easter eggs in some games in last years easter event?
Older games were givin eggs and you were given clues to find them, so we know AG can edit games (or have the devs) at will.
AG had to have some connection with the devs if the eggs suddenly appeared and formed a message.
But, there was nothing in the news so its probably an easter egg.