Giles,
The regulations, and the Vernet plates which were sent to units to illustrate the new uniforms, show no red piping on the turnbacks. However, this being the French army, who knows what actually appeared! I am sure that one could argue that the occasional unit with red piping is justified by the colonel being a bit of a traditionalist.
As an aside, I always feel rather sorry for the French colonel who, on the issuing of the white uniform regulations, went out and had a new white uniform made, and had himself painted in it, only for his regiment never to receive the white uniforms.
I would be interested to hear your technique for such fast painting. Very nice indeed.
Best
Ben