It is very logical.
This blue dope is an experience. Somme of them were blue or white (see Marc Chasard works about it).
in the 8xx serials, most of Nieuport were camouflated and did not wear roundels.
So those planes did not neither.
See the Tarascon plane in the same case

this one is white and the the others are camouflated
So was the Chapman's plane in the lafayette squadron for example...
Xan