Many thanks for the kind words and encouragement, guys.
Regarding colours, I always think of McCudden's reference to a 'silvery blue' triplane, doubtless an effect of the strong sunshine at altitude. When I'd finished brush painting the green streaking, I felt the overall effect was a little dark, so gave it the lightest misting of a white top coat which happily gave me exactly what I thought JTB McC meant!
S
PS tried re-optimizing pics. Not sure if these are any better, still rater grainy I'm afraid