What stars were Jews required to wear?

It was a six pointed star, often called the Star of David,* in the Nazi period it was required to be yellow in color.

Note

* The term Star of David is more commonly applied to a different symbol, of which you may see a version on the Israeli flag, a six-pointed star consisting to two overlapping triangle outlines. The yellow star that Jews under the NAZI regime were compelled to wear on their clothes was a filled-in yellow six-pointed star quite different from the magen David.