If it isn’t gums oxidizing, it’s the cannabinoids or cannabinoid-like byproducts of the distillation. That’s generally the rose color people see in very pure almost colorless stuff, and yes, it is purple if exposed to basic pH at some point during processing. I believe this pink color is the formation of quinoids, which are oxidized cannabinoids that actually have extra oxygen atoms attached to them at various sites on the molecules.