Antisemitism--Jew-hatred or Judophobia--has been around as long as Jews.
Why "IN YELLOW?" It was the most common color of the badges and clothes Jews were forced to wear in Europe and under Islam. After repeated expulsions and permission to re-enter into various countries (for economic reasons not for "love" of Jews) during the Middle Ages. European anti-semitism continued.
The yellow clothes and badges were designed to make the Jew an outcast,and marked him for ready identification for persecution. The yellow was only a garment, it did not reach into the Jewish soul. Jews were beaten, imprisoned, and killed with impunity. There was only one answer to this persecution and hounding from country to country: a country for the Jews. A land where Jews would no be persecuted by their fellow citizens for being Jews.
Israel the land of the Jews came about by in large part by Jews who were not reticent to take action. Prominent amongst these were the fighters of the LEHI (Stern Group) who did much to sour the desire of the pro-Arab British not to have a Jewish country.
“What we dream of is—Jews strong enough and honest enough to hate their killers …”
"Finally and long overdue, your people, oppressed and disgraced by hatred and maliciousness, have achieved justice: now you enjoy full citizen's rights, but you'll remain Jews nonetheless." --
--Franz Grillparzer (1791-1872), Austrian playwright.