The photo credit indicates the picture was taken on June 6, 1973 (http://www.gettyimages.com/detail/news-photo/oakland-athletics-reggie-jackson-in-action-at-bat-vs-news-photo/108898985)
While SI did not use the Reggie Jackson photo, two pictures from that day were included in a Sports Illustrated article in the June 18, 1973 issue:
Here is an uncropped shot of the Gene Tennace photo which better shows the green pants
and here is a shot of Ray Fosse that was not previously published:
According to Dressed to the Nines, 1973 was the only year they wore this combination:
and the Indians all red combination
the 1970's provided some very memorable monochrome combinations that we rarely ever see today. Love them or hate them, they definitely stand out.