Ears: salt and pepper grey/white with beige/white insides. The tips stay black though.
Hair: PREMATURE GREYING AT AN ALARMING RATE but the tips are still dark so it's kinda ombre-- I can't believe I just described a matsu's hair as being ombre
Tail: more of that salt and pepper grey look. The tan underside starts turning white and looks beige-ish
All other fur: grey/white/black
He begins growing a lot more fur, including the start of a fluffy "mane" around his neck.
This is probably the best way to imagine the look of his coat, but there's no direct inspiration for it.
Note: this form is being mostly skipped (or at least significantly shortened ) for 2017 so I can still have him be his summer look for a while (since he JUST changed). He'll start doing this more properly come 2018.
Winter
Ears: pure white inside and out with black tips
Hair: white, save for the tips which, like his ears, have remained black
Tail: completely white
All other fur: white, with beige on his fingers and feet where the tan had been. Some black tips are present on his neck fur.
Fur coat is a lot thicker.
SUPER fluffy. Like the floofiest you can imagine. Especially around his neck, where the "mane" is now full and covering the whole thing like a scarf.
Skin's a little paler, just to help blend in with all the white.
SEASONAL
Fall
Winter
Spring