Hey Harry, didn't know you were interested in "our" birds...
The Mustang in question was not really captured, it landed on Yugoslav territory due to the battle damage and was abandoned by the pilot. Yugoslav mechanics repaired the plane to flying condition and she received improvised red star insignia. As you can see on the profile you posted its all original US insignia with one difference - white stars are over painted with red color. Otherwise nothing else indicates Yugoslav Air Force.