I don't think the Packers have toyed with an all green uniform, including helmet.
Unlike most of the posters here I really like the all-white look, including the new helmet. I also agree that these "changes" are designed to sell outrageously-priced and NFL-endorsed merchandise. As such, they're gimmicks. Now this is a very good example of greed by the NFL. Create a uniform for one game, and sell tons of new merchandise from it. Although they've played in white uniforms before, so not sure what the white helmet adds to the NFL coffers. As if they need the money anyway.
Like it or not, it's only for one game and it's a gimmick.