Winter’s Clothes
First, two notes:

One:  I think that Winter engages in a combination of actually knowing how to tailor his own clothing and using strand-working to make everything lie Just So, because I do not picture any of the RoundTree siblings particularly rich (Summer might be, eventually, but who knows?) but damn, the man dresses like a million bucks.

Two: I started a Pinterest page for these RoundTree-Family clothing images and anything else that strikes me as being Very Stranded. 

https://www.pinterest.com/aldersprig/stranded-world/ 

Now on to Winter.  Winter likes to dress very nicely, very tidily, and very professionally.  His impeccable dress and his neatness have led some of his co-workers to speculate that he’s suffering from some sort of Obsessive-Compulsive disorder, but Winter is no more disordered by being centered on Order than his sister Spring is disordered by being centered on Chaos:  That is, they like chocolate, but they can stop eating it without an effort. 

Winter, Every Day, above and below.
(Source 1 ; Source 2

Although Winter probably indulges in ties with lovely, complex knots, as so:

(Source

Winter when on a casual day, above and below (I imagine the denim is when around his family, tbh).

(Source 1; Source 2)

And there you have it!  Winter, his style from day to day. 

He has, by the way, perfectly-white hair in a very tidy ponytail that goes halfway down his back, and has had white hair since his late teens.