If you look at photos of Jews back in old Europe pre-Holocaust, you will see that most of them are not wearing black hats; most are wearing gray hats.
Yes. This is correct. If you look at pre war photos of bochrim from the Chofetz Chaim’s Radin Yeshiva most are wearing gray fedoras. Even rare pictures of the CC show him wearing a cap. This black hat custom is an American Yeshiva modern Orthodox thing probably started in Telshe or Lakewood. Definitely no mesorah for it from the alte heim.