First of all, dogs are not afraid of the color black! It is true they are color blind but they are as likely to run from or be drawn to the color white as they are to the color black. And studies show they tend to like bright contrasting colors like purple on red. So, what's up with the strange "dogs hate blacks" comments? Even my friends who claim to be liberal and are not racist seem to have color issues.
This is my take. Dogs are extremely intuitive creatures. They pick up not only the vibe of their owners but also those of strangers. Bottom line is, if you have issues with dogs, like growing up in countries or areas were dogs tended to roam wildly or in neighborhoods where they were used as security behind gated fences with signs that read, "BEWARE OF DOG," you may be scared shitless of dogs. If you were bitten by a dog, no doubt you'd be tense in the presence of one. Dogs react to this and some will bark.
Dogs also vibe of their owners. If owners have "color issues," their dogs will definitely pick up on this and more than likely bark at the unexpecting brown person. But, oh, how convenient it is to project one's feelings onto a dog that does not speak. Convenient indeed.