I noticed that, but I just figured it'd turned some random person with a dyed streak in their hair. Because otherwise it makes no sense - nobody else has retained any part of their natural colour, why should this person? (Heather, for example.)
Given that it WAS mentioned as something new, something different, I don't think it can be put down to poor research. The writers obviously know this isn't how it used to be.
These Wendigis are more like werewolves right now. (This isn't a complaint, just an observation.)
That isn't an argument! It's just contradiction!