Welcome to the party. I hope you remembered your chicken suit.
One thing I noticed about this mission after watching the tape is that the chicken suits serve an second purpose, other than just being a joke.
When you consider the massive crowd roaming this space, you realize that the designers needed a way to separate the NPCs that have an effect on the mission from the ones that don't matter at all. It's easy to do that with the police officers and the waiters, since they have their own uniforms and large exist on the outskirts of the crowd. You'll see those guys in plain sight anyway.
But what if you need to make an NPC visible enough to spot and tail at a glance, like the diamond deliver guy. Well, a chicken suit that goofy and flamboyant stands out among the otherwise nondescript NPCs that are scattered about the area.
Or if you choose to not tail the delivery guy and instead look for Mark Pariah's base on your own, then we need another type of chicken suit so that you can spot your destination once you've arrive. This is where the yellow chicken suits that the target's guards wear come into play. Since they are only in the one building, their presence can tip off an observant player.
At the same time, we can't have the actual targets blend into all the other chicken suits. I/O Interactive needed to give them their own color palate. This is why they have black chicken suits. As a bonus, they can use the crow motiff for a punny title.
And since this contract takes place during Mardi Gras, the player won't even question the fact that these guys are all running around in chicken suits. It even adds to the charm of the universe that something so silly can just exist.
And thus, the iconic Hitman chicken suits were born...