Thanks for turret foto. It helps.
Here you will find interesting discussion regarding stained plywood:
http://www.theaerodrome.com/forum/sh...ad.php?t=41832
Basically german could have used yeallow or orange shelack. Reports about bana mens come out from Albatros DII fighter apperance which had green wings and fuse stained with yeallow shelack prior to varnishing. I personally used orange one for CIII. Í m curious if it will change shade after some time.
Another info regarding design and build of german aircraft you can find here:
http://www.craftlab.at/index.php?id=38&L=1
http://thevintageaviator.co.nz/projects/aircraft