As far as i know, Serbs are I/E haplogroups making them eastern Med, Anatolian with 1/3 integration with Europeans (north black sea/north sea). We are not clear on whether southern I/E’s are from east black sea, Aegean, Anatolia, or Levant. So technically, they are a borderland admixture. But they are the remains of a very old people (big, strong) who are not white in the sense of R1a/R1B but West eurasian. I’s ranged north south but were split by the european horse rider expansion.
https://www.quora.com/Why-do-Serbians-not-consider-themselves-white