Sometimes a perceptive #avgeek can tell which airline an unpainted new plane will be going to. The rudder gets installed already with final paint because the paint hangar can't get inside the mechanism with out disassembling it, which they don't want to do. Unless it's a special livery, this looks to me like it's going to Singapore Airlines.
Credit to @JetTip for the first hint that a Boeing-owned plane might be on the way to Portland from Renton, which I inferred as possibly new. #aviation
@ikluft Just having the rudder painted makes it look like a RAF fin flash.
Is it just easier to paint the rudder and then mask off the hinges?
@simonbp The tour guides at the Everett factory public tour tell guests the reason. I first heard it at the Aviation Geek Fest tour on the factory floor.
The two reasons they paint the rudder first are to get the exact weight of the paint and they don't want to disassemble the rudder (or anything) at the paint shop to get at its hard-to-reach surfaces.