Look at the holes in the two shakers. If one has holes larger than the other, judge accordingly if you want more pepper or more salt to shake out. It seems to me that the larger holes would be your salt shaker. Of course if the holes are the same size in the shakers, I'd use the red one for pepper and the yellow for salt. Dumb? I dunno, but here's my imput, for what its worth. Good luck in deciding. Toss a coin?