On the black dog syndrome

I have read from time to time of the Black Dog Syndrome, which is probably a myth. It is interesting to think about why would there be a preference for or against a dog of a particular color, and how could it ever be proven. This topic is also of interest because of the three dogs I have owned since 1991, Ladybug (2010 - present), Chrissy (1991 - 2006), and Jenna (2007-2008).