That still wouldn’t account for the genetic differences between the skin color/ hair color of the Seam and the skin color/ hair color of the Merchants.
As for how she identifies as a person of color, as the thing I posted earlier said:
"“Katniss may not be able to be “classified as Native American or Latina or mixed-race,” but she has been CLASSIFIED — and self-identifies — as racially, ethnically, and culturally Seam, and makes that a huge counterpoint to her view of Peeta, who she classifies as racially, ethnically, and culturally a Merchant. No, Panem does not seem to have the same racial markers (or ethnic, cultural, or religious markers) as we do. That DOES NOT MEAN that they don’t exist, and DOES NOT MEAN that they should be ignored when we ARE given their differences in the text. We don’t know HOW dark the Seam’s skin is. But we know that it is pointedly darker than the Merchants’ and that has made a significant, significant difference in how people are raised, married, treated, and receive job placement in D12.”
That is how she identified as a person of color. To me, this is the most compelling argument.
Seriously, google “olive skin” and tell me why 99% of the people who come up are people of color.