Bo, I know, right? However, this is something the Alan Toelle says is unique to Nieuports, and not other a/c such as SPADS, Salmsons, Voisins, etc. To be honest, I prefer the lighter, duskier blue, it's more pleasing to my eye. Nevertheless, I can see the logic in what he's saying based on the evidence he presents, photographic images, etc.
A well known autochrome bears out what Mr. Toelle says here, at least IMHO:
![](http://i242.photobucket.com/albums/ff12/dixieflyer500/Nieuport%20Stuff/Nieuport%2017%20color%20shot_zpsoly9p9qn.jpg)
And here:
![](http://i242.photobucket.com/albums/ff12/dixieflyer500/Nieuport%20Stuff/chaput_zps8ljrfwnf.jpg)
Petrov, the relevant articles are in WS vol. 23, no. 5 and no. 6.