Green Bean:
Do you mean “Why did so many Jews end up with German color names as surnames, seemingly more so than German speakers in general?”, the answer would be that Jews functioned quite well without surnames for several millenia until required to assume surnames, in the local language, by the authorities in German-speaking areas of Europe in the late eighteenth and early nineteenth centuries (until that time, Jewish names were of the form “<name> <patronymic>”, as in “Yosef ben Yitzak”, meaning “Yosef, son of Yitzak”).
While many Jews were able to adopt names related to their occupation, place of residence, etc. (mirroring the circumstances that led to most Christian surnames), others were forced to contend with mean-spirited or greedy minor officials who registered surnames based on how large a bribe was provided. Names with positive connotations (Diamant, Rosen, Blume, and most of the invented combinations of -berg, -stein, -feld, -baum etc.) went to the well-off. Officials who were more honest or too busy to attempt to line their own pockets often made do with a relatively small group of more-or-less neutral names, often based on appearance (size, hair or eye color, etc.): Klein, short or small, Gross, tall or large, Schwarz, black, Weiss, white, Gelb, yellow or gold, Braun, brown, etc. Other German color names, like Gruen, green, Blau, blue, Rot, red, and so on occur less often by themselves, though they’re common enough in compounds: Gruenberg (aka Greenberg), Rothschild, etc.
“Ain’t no man can avoid being born average, but there ain’t no man got to be common.” –Satchel Paige