By inner, do you mean inside the nozzle? The inside should be white, though they get pretty dirty. Check the photo gallery here for the jet you are planning to build, that should help you too.
Sorry for not expressing me properly What I meant was the part closest to the body (the part I accidently painted silver), which I guess should be grey as the body, or?
Nice work soo far.I must say that this is one of the best models that I have seen in a long time. The pieces are formed and fit with an amazing amount of precision and this turning out to be a beautiful model.