I have a '14 Sierra and it is doing the same of both doors, the hood from rock chips, and the bed of the truck is peeling like crazy.
It is Metallic Silver. I recommend anyone looking at buying a used '14 Sierra RUN as fast a possible because the paint job of these trucks is horrible.
I have tried to mitigate this the best I can with touch up paint and covering the affected areas to prevent it from spreading but it is only a matter of time before that happens.
I love the truck and mechanically the truck is sound but I am severely disappointed in the GMC paint job.