Currently, the new Werewolf only has three textures: Ashen, Black, and White (this one looks distinctly albino rather than arctic). Ashen has a brown tint and is used on the base morph, Black is used on Berserker, and White is used on Pack Leader. You can unlock Skill Styles starting in Season One to change your fur color to be different from what your morph defaults to.
We also know that ZOS intends to update the werewolves in the game to use the new model. We see this with the updated Hircine's Gift quest, where each of the werewolves there use the new model and one of those three aforementioned textures.
However, the original werewolf model (not counting the undead model) has
five texture variants. In addition to brown, black, and white (which we see translated onto the new werewolf) there's also gray and "dark black".
I consider the new black fur texture to be an adequate replacement for both of the old black fur textures — any old werewolf using either the black or dark black fur texture can be changed to use the new black texture when updated to the new model. You primarily see werewolves using the dark black fur texture in Moon Hunter Keep, which is getting a Solo Dungeon variant made later this year.
However, what will become of werewolves using the gray fur texture? If the update to the Hircine's Gift quest is any indication, they'll switch to using the brown-tinted "Ashen" fur color. But what about encounters where there are
both brown and grey-furred enemies?

These werewolves in Blackreach Caverns use the brown and grey fur colors to distinguish which one is the stronger enemy. This is one of the only instances in the game where an enemy is using the brown fur texture, as that used to be primarily reserved for player characters only.
I've always liked the grey fur texture that the NPCs get to use, and I'd like to be given a style to make my Werewolf characters have grey fur. I hope we get a grey fur texture in general so that encounters with werewolf enemies can be updated while still retaining their original fur colors.
PC/NA — Lone Werewolf
Werewolf Should be Allowed to Sneak Prowling added in Update 50!
Please give us Werewolf
Skill Styles (for customizing our fur color) Added in Update 50!,
Grimoires/Scribing skills (to fill in the holes in our builds), and
Companions (to transform with).