Flatbusher, what do you mean my reasoning? it’s a halachah in Shulchan Aruch, and the Igros Moshe which old man quoted (which I linked) says outright that the medication (vitamins?) which he assered restored the original color.
If you want to be dan the individuals you see l’kaf z’chus, you can assume they did it to get a job, which R’ Moshe is mattir if there’s no ona’ah.