So, one thing to consider is that sub assemblies (like tails, control surfaces, wing tips, etc) were often built and painted by a sub-contractor and then delivered to Boeing, so it is very possible the olive drab on the airframe and that on the tail did not exactly match even before delivery to the USAAF. Even at boeing, the plane was not painted all at once, but rather in the sub assembly stage, and paint variations are possible even within the same plant as new batches of paint were going to have to be continuously delivered or mixed (rare for two batches of paint to match exactly)
then also unit markings on the tails changed several times, even for aircraft that stayed in the same unit, and doubly so for ones that got repaired at a depot then sent to a new unit - more chance of fresh/different shade of OD on the tail
concerning the rudder: paint on a fabric often looks different (darker or lighter, depending on the angle of the light) because more light is scattered by the texture of the fabric than by the metal panels. add to that the fact that even a few degrees of rudder deflection, which is common during a bombing run (that is how the bombardier guides the airplane since you don't want the plane tilting while you are releasing), will also cause light to reflect very differently (and make the rudder appear darker or lighter).
and apparently this aircraft had tail damage at some point because of the NMF tail gunners position - a new (or repaired and repainted) rudder might have come with that, and fresh OD is noticeably darker than one that has weathered even a little (though admittedly, the repaired or replacement rudder could have also been painted dark green)
the result - I bet (but don't guarantee) the rudder is actually also olive drab - going with another shade of olive drab on all the fabric surfaces is almost certainly your highest probability of accuracy. note how the ailerons look darker than the flaps even though they are at the same angle - i guarantee the bottom of the ailerons are not painted some color other than the neutral gray the flaps are in.
your model will look most interesting if you go for several shades of OD (or even dark green), and no one can say it is wrong, esp with such a difficult to interpret picture as proof. just as likely the whole aircraft was nearly the same OD color actually - that picture proves very little other than the light was playing on the different surfaces in various ways - differing colors is only one explanation for why that might be.
speaking directly to the picture and the tail unit (not rudder), hard to say - sort of looks like some other olive drab might have been used, but i'd actually say it ended above "joker" rather than going all the way to the base as the profile painting has it. but also consider the picture the profile artist used to work from is probably a lot clearer about showing shade differences than a scan of it found on the internet....
basically, whatever you do isn't going to be easy to prove wrong or right.
