It's going to be pretty difficult to tell you one way or the other from these photos. There are a TON of fakes out there. They are generally real helmets that have been repainted and artificially aged, but there are actually new made helmets out there too. Yours may have been painted as a type of winter camo, The soldiers used anything they could get their hands on so the color isn't out of the question...... Your best bet is to try the Wehrmacht Awards forum. The guys there are pretty good at determining if something is original or not.
Wehrmacht-Awards.com Also, there should be another stamping above the 5 digit stamp you mentioned. It should be two or three letters and two numbers. That will be the makers factory code.