Brown

And more of it.  I once read that crewneck sweaters are more preppy than v-neck sweaters because crewneck sweaters only incidentally show the necktie, as compared to v-neck sweaters, which are designed to show it.  The thinking goes that only the nouveau riche feel the need to go out of their way to show off how fancily they dress.  Me, I have them in both styles and like them for different reasons.  V-neck is more appropriate for wearing with a suit anymore as it's pretty much bog standard among lawyers and probably bankers, so much so that wearing a crewneck with a suit and tie would possibly look like an error to someone who didn't know you.  There be dragons.