There are styles of dress which are quite iconically jewish that to most observers may cause a person to mistake someone as jewish.
Each part of dress in the upcoming list on it’s own may not cause someone to mistake you for being jewish but certainly an ensemble which includes a few of these features together should be avoided for a Noachide.
Any list of jewish dress cannot be comprehensive, the following list is a broad generalization of the features of dress which are most unique; that to an observer might cause confusion as to the persons religious observance.
This list is mostly in regard to men, if it is requested I could add women’s dress.
Kippah or Yamulke.
Wearing a Tallit (prayer shawl).
Tzitzis (fringed garments).
White dress shirt with black pants. White dress shirt with a black jacket. Long black coat.
Black shoes with visible white socks. Rimless glasses especially with a titanium frame. Black framed
glasses, especially oval or circular.
Circular glasses and a full beard longer than 2 centimetres.
Wearing a short scarf over a jacket.
Wearing a scarf in any season
other than winter. Wearing a scarf indoors. Any display of jewish
symbolism like the Star of David or Menorah or a pattern with such
Blue tie with a white shirt and black pants.
Carrying or wearing a Tefillin or Phylactories (leather black box and strap).
Payot, the long hair just on the sides of the head. Long full beard esp
with uncut corners. Long beard with short hair. Long beard with long
hair. Long beard with a black hat.
A simple way to dress in such a way that would avoid confusion would be casual western wear, western in the cowboy sense. Plaid patterned shirts, blue jeans and brown boots. You could wear any shirt with snap front pockets or embroidery on the chest without a jacket or with a bomber jacket.
You can wear coloured slacks pleated or not with brown shoes or boots.
For a hat you have many options. You could wear a brown wide-brim hat, a baseball cap, a woven or staw hat, a coloured ascot cap, beanie, or even a french beret.