Great question James! That apparent discoloration is supposed to be there, and actually makes the case better. Lake City brass is annealed, or heat-treated, around the neck to make the case more supple. This provides two beneifts. First, the casing is better able to seal the chamber off from the barrel during ignition. That makes ignition more efficient, and combats chamber fouling. Second, annealed brass is more durable to suit it better for handloading.