I also read about black dogs being passed up in shelters. When I was pregnant with my first child, I had a black lab/german shepherd mix named Peewee. He was amazing!
My first husband and I worked weird shifts - I came home to an empty house at 10
m. I got home one night and PeeWee came running up to the car (my first clue - he was OUT of the house) When I tried to get out of the car, he leaned against me and absolutely would NOT let me enter the house. He actually growled at me and kept pushing me back to the car.
I finally went to the neighbor's house (before cell phones in 1975) and her husband walked with me to the house and, yes, it had been broken into. Nothing was taken, and I don't think the burglar made it into the house - the bathroom window was broken and open, but you could see on the wall inside where Peewee had scratched it up going after the burglar thru the window.
Peewee was my hero! When my son was born he thought the baby belonged to him! My son learned how to walk holding onto his collar and he was a great babysitter!
I know this is long - but I believe you can have a great guard dog and also a beloved family pet at the same time.
Good luck in your search.