@aisnya, By far, most Jews and throughout the 20th century if not further back are descendants of European and Caucasus communities that migrated from the Middle East beginning prior to 1,000 AD, which, I assume, accounts for the differences in skin tones as gail suggested.
From http://en.wikipedia.org/wiki/Jewish_ethnic_divisions:
Despite this diversity [of Jewish ethnicities] , Ashkenazi Jews represent the bulk of modern Jewry, approximately 70% of Jews worldwide (and up to 90% prior to World War II and the Holocaust). As a result of their emigration from Europe during the wartime periods, Ashkenazim also represent the overwhelming majority of Jews in the New World continents and in countries previously without native Jewish communities, such as the United States, Canada, United Kingdom, Argentina, Australia, Brazil and South Africa.