I would vote for International Orange - ya gots to wear orange when you go hunting, right. If the argument is - hunting or even target shooting - what would be wrong with that.
As I think about it, and I'm not really joking, I might be just fine with AR-15's, 20 round clips and the rest if they were all Hot Pink or Neon Green or International Orange. That alone might stop most shootings.
Don't care. Had to carry my shot records everywhere I went in the military. Along with my military ID, driver's license, military driver's license, etc. I'm not sure why this "passport thing" is turning out to be such a big deal.