Hello,
Thanks to everyone for their responses.
There are some photographs and a colour profile of N1831 in German markings at:
https://www.pinterest.co.uk/pin/291959988326149761/
and speaking of Nieuport machines in foreign colours there is a photo of Italian Nieuport 17 N3242 (at least I assume that it is both a Nieuport 17 and Italian) at:
https://www.ebay.it/itm/Grande-Guerr...UAAOSwRsJeVZV0
and some less clear Italian machines here:
https://www.ebay.it/itm/n-2-foto-WW1...cAAOSwa5Rd~-m0
Regards,
Clint