wrf,
If you ask this question on The Aerodrome (
www.theaerodrome.com) you will find out where the "experts" hang out. There are some guys who live for questions like that and who really know their stuff. Unfortunately, a lot of them talk in terms of Methuin colors, but that's useless info, since nobody seems to know where the Methuin handbooks are or where you can get one. Most have been out of print for a long time. That said, the Aerodrome is worth a look.
When it comes to colors on WWI models, do your best research and go with whatever colors look best to you. Nobody can prove you wrong.
papermache