illusion

Most definitely painted, given the clear line of demarcation, and reflective differences. A little bit of research turned up that 95th BG B-17s has stripes added to their nose sections around July '44. Specifically, planes from the 334th, of which "Worrybird" was assigned had a yellow stripe. This makes sense, given that the color looks like a brighter hue... minding that many colors look widely different in black and white, depending on a number of unknown factors. Regardless, photos of other 95th BG B-17s online also show red, blue and green, which matches this reference:

https://95thbg.com/cms/2019/12/6/camouflage-and-markings

Scroll down to "July 1944" for the correct notes.

1 attached image. Click to enlarge.

A painted stripe in the "squadron color" was frequently used on B-17s for additional identification. That's what this is.

One more photo of Worry Bird.

2 attached images. Click to enlarge.