Black has a negative connotation because of its association with death. That is in fact the origin of the term "blacklist" - a list of people associated with the execution of Charles II's father. It's also the origin of the term "black day" - a day of death and, by extension, disaster.

While this association is not in any way "natural" or necessary, and it's not even universal, it is still extraordinarily old - dating all the way to Ancient Egypt and influencing European culture from there to now. And thus, it is extraordinarily hard to remove by playing language games with one word.