In fact, if I had to go on color, I'd pick a black dog over any other color. In my opinion, black dogs look regal & elegant, more ''serious'' if that's the right word. My dog is solid black & he's beautiful.
I think it's partly superstition - many people still, stupidly, believe the old tale that black animals are ''evil'' or ''bad luck'' - same goes for black cats. A year ago, when I went to visit my local animal shelter - most of the cats were black or black and white. On the other hand, I've heard that people think black dogs look more ''vicious'' or tend to be more ''aggressive'', which is bull.
I also suppose that people might consider black a ''boring'' and ''dull'' color, and not ''pretty'' - therefore might prefer brighter, more ''welcoming'' colors such as Yellow, Brown, White, Tri etc. I suppose black doesn't stand out as well in a shelter row, as a bright yellow dog does.
I love black dogs the most - they're beautiful. I love the coloring.