Agreed, Gaz.
I took the liberty of sampling small areas of the various features to see how they compare and contrast, against both white and black backgrounds. Certainly doesn't inform any particular color decisions, but simply indicates the lightness or darkness of certain areas compared to those features assumed to be either black or white. It looks to me like the Jasta 54 'Saxon' conclusion fits nicely within the parameters suggested by the samples. I also note that the thin borders on the edges of the personal motif don't appear to go over the top of the fuselage. Given the effects of light, shadow, and the behavior of those early film emulsions, one could advocate for darned near any combination of light and dark colors. Great subject choice!