No, it can't be diet related, Den, because the feral group I work with are always fed the same diet, year in, year out.
This year the cats coats have stayed darker than they were compared to last spring/summer. Last year they looked like they had been rolling in fake tan.
It was Reynard who first explained to me about the reasons why black cats turn orange and vice, versa.... haven't seen Reynard in these parts for months and months.