When I read On Blondes recently the author noted that in a 1930s survey of Jewish schoolchildren the Nazi regime found that:

• 10% were blond haired.
  
• 50% were mixed hared.
  
• 40% were black haired.
  

Last year David B. emailed me the following data on 19th century Anglo-Jewish eye color:

• English Ashkenazim: Blue 11.1 Grey 30.1 Brown 58.8
• English Sephardim: Blue 21.3 Grey 11.9 Brown 66.8

David noted "...But the striking thing is that in both cases the blue/grey proportion is over 30%. Since blue/grey is recessive to brown this implies a majority of blue/grey genes in the gene pool."

I don't know if the German study included mischlings (mixed children), but I began to think about this again when John Rethelford in Reflections of Our Past refers to Hammer's paper that suggests that Jews genetically reflect more their Middle Eastern ancestry as opposed to converts from the populations among whom they settled (Rethelford is himself a convert to Judaism). So....

1) did Jews pick intermarry at a non-trivial rate?
2) was there selection for "fairness" in the European Diaspora?
3) was the source population blonder and more light-eyed than we imagine Middle Eastern populations to be? (note that Yemeni Jews do not show the introgression of African mtDNA that is noticeable among the Muslims around them-likely because they became genetically isolated during the period of Islamic slavery).

Here is an old post with many links to studies on Jewish genetics.