1980 Packers

http://bleacherreport.com/articles/867077-the-5-worst-chicago-bears-losses-to-the-green-bay-packers#/articles/871819-panthers-vs-bears-6-keys-to-a-chicago-victory

That is a link to photos from the first 1980 Packer-Bear game from 1980 where the Packers' kicker, Chester Marcol, ran a blocked kick in for touch down against the Bears. Local media has done some stories about him this last week and I have watched some of the old video clips. If you look at game throughout the season, some Packer players were using green masks and some were also using grey.

To a much lesser extent, this is similar to the problem we encountered with footwear. Back in the 60s and 70s, teams were slowly transitioning between black cleats to white cleats. In one year a team would be split 20-80, then 40-60, then 70-30 until the entire team was in white cleats. Rather than show combinations for both shoe types during this time we decided to go with the majority. When the majority changed, we changed.

Now facemasks were a little more abrupt of a change. I'm guessing based on the photo, that the grey may be limited to only a few players with 'unusual' face-gear - like Chester's single-bar there. Couldn't they have painted his single-bar green to be uniform? Sure. But I don't think that the NFL's uniform police had been created as yet.

1980 is the year that we changed GB's facemasks to green and I'm sure waaaaay more players had the green than the grey.