Why should I ever go green?
It depends on the setup. If you've got Bat Milk, and a few other deck thinners, you remove all of the other trash from you deck, draw your entire deck every turn, and win before anyone else has really started.

Green has the majority of the deck thinning cards (and PVP Defense). Also most of your combo cards are going to be in green. Werewolf in a Tophat and 3 Natural 20s = 3 of each boss loot all on the same turn. With Bat Milk in the mix you can do that reliably.

On the other hand, sometimes Red IS the better choice. Again it depends on the setup, and how other people play. Having some Defense or Deck Thinning is vital if you have a lot of people buying PVP attacks.