re: Crackpot ASOIAF Theories SPOILERS

I think Lyanna was described having dark hair. Generally, if you mix dark hair with light hair, the kid comes out with dark hair, unless the dark-haired parent also carries a light-hair recessive gene (which would still leave the odds of a blonde kid only being 1/4).

Also, I'm not sure if Jon's hair was actually black in the book. It may have just been dark brown.