Spectra Shot manufactures 12 gauge waterfowl and skeet ammunition that features colored shot. The idea behind colored shot is that if two waterfowlers each use a different color, they can easily distinguish who shot which bird.
I would have thought that finding bird shot inside a feathered sack of meat would be tricky. What do veteran waterfowlers think? UPDATE: The experts (in the comments below) say it is pretty easy to find the shot.