Having seen this old thread coming alive again, I checked the latest publication on Voss and his aircraft (or better: the latest I am aware of), that is Bronnenkants 6th volume in his PLM series, covering Thomsen, Hoeppner, and Voss, published earlier this year (2015).
There are long discussions about why his DIII was always the same aircraft (means: instead of two different aircraft, the "early one with two red hearts", compared to a possible "later one with three red hearts") - it is the same aircraft, form the first production batch. Bronnenkant (and Jim Miller, who did the photographic analysis) agree on an upper wing replacement due to the shifting of the radiator. It is discussed at length when the third red heart might have been added to the fuselage.
But (and that I think is the most important part wrt this thread): Not a single word is lost on a possible repaint of the spinner when Voss was shifted out of JaSta B on May 20th,1917. Bronnenkant thinks the spinner was black and never changed.
Stefan