I've looked into this, and Great white is actually a Kolsch (sp?) ale. And as it says on the bottle, it is brewed with "Coriander, and a secret blend of humbolt spices." For those of you not familiar with Northern California, Humbolt is notorious for it's prolific production of,..... well a lot of people mistakenly think it's related to hops.
I've had it. Wits aren't on my hit parade though, I like Downtown Brown much better. You might try this recipe. MadBrewer's Spiced Wit Ale I would not be surprised if Chamomile is the main secret, it adds a very nice smoothness to a beer. I use it in ginger beers.