Thanks all.
So this is the state of play as of Tuesday morning. Much hand wringing....
Look at the tail coverings compared to the wings..

Both the plywood covered and the fabric covered areas are much, much darker than the wings or anything else but they DO match the fuselage.

So, after consulting with my better half and much more hand wringing, the upper parts of the empennage were lightly coated in Prussian Blue.
That's my story and I'm sticking to it.

The arrow decal is much too short but I'm not wanting to cut masks and airbrush and blah, blah, blah so it's staying short.
Sadly, life is getting in the way for at least the next week. A Florida beach with two chaises is calling us, be back in a week or so....
Thanks for following along.