|MadSci Network: Genetics|
I am going to refer you to the following recent answers of MAD Scientist Network questions on Pigment/Melanin in Skin/Eyes/Body, from Dr. Gil Stoewsand of Cornell Univ., & Lightbrown Eyecolor, from Tom Stickel of Indiana Univ., which address this topic in detail.
Thank you for the good question,
Jeff Buzby, Ph.D.
Children's Hospital of Orange County
Try the links in the MadSci Library for more information on Genetics.