Gilles,
Thanks for another reply. I could see the difference in shade, but I wasn't sure how much might be due to the space between the feathers.
What I have been been using so for is red most for early planes based on Guynemer's SPAD in Paris, and white and black for SPAD XIII's.
I can see looking at my results below, that the plummage is not very different than the body, though part of this may be the gaps between feathers being too narrow.
I hope DeltaK does not mind me posting the results of my modifying his patch?