There is much discussion regarding WW1 German camo helmets. This is my belief:
1) Disregarding modern (by modern I mean 1960's to now) fakes, I believe the vast majority of them were painted during the war. The number postwar souvenier painted pieces is greatly overestimated.
2) The helmets were not painted by the individual soldiers, but by details at some organizational level (platoon, company, etc) while out of the line.
3) Some helmets almost appear to be factory done. Over the years I have seen some helmets done very nicely, with very smooth paint, always in the same colors and in the same style, kind of a swirly design. These were probably done at a higher (corps?) echelon. I am haunted by one of these I saw in the early 70's that had an MGSS insignia painted on it. No, I didn't buy it.
4) Regarding colors, they used what they could get. Regulations are fine, but Germany was short of everything in 1918. Unless the colors are completely garish, it's OK.
5) In my 40 plus years of looking, I would estimate maybe 10% - 15% of the many hundreds I"ve seen were camoed,
6) One reason photographic evidence is scarce is that retreating armies don't have time or inclination to take photos. I have studied WW1 since I was a kid in the sixties, I have seen very few photos from the German side taken in the Argonne in 1918. However, I have read more than a few doughboy accounts describing camo German helmets. There's a passage in Woodfill Of The Regulars where he talks of picking off a German MG team wearing them.
7) Having said all that, modern fakes are so good they are scary. Even the "one lookers" need a second and third look. I won't buy them anymore unless it's from the doughboy's attic.
There. I've thrown the bomb. Agree or disagree, that's my story and I'm sticking to it.
Steve