I'd guess the two biggest hits for the Brothers Four were "Green Fields," and Green Leaves of Summer. I don't believe they had anything to do with Green, Green, Greenback Dollar, or It's Not Easy Being Green.

"Green Fields" was written by Terry Gilkyson, Richard Dehr, and Frank Miller. It was first recorded in 1956 by Terry Gilkyson and the Easy Riders, and it was a hit for the Brothers Four in 1959.

Collectors' Choice Music has a number of Brothers Four reissues on CD. I have four Brothers Four CD's on my shelf, right next to They Call Us Au Go-Go Singers.
What can I say?

-Joe Offer, not a folk purist-
(I sent Ebbie a recording of "Greenfields," but it wasn't the right one)