Magick does not have a color, it is neither black nor white, the common way to put it ive heard is to say that magick just is. but any of you who know that probably didnt come here to just reaffirm what you already knew.
As an alternative i GUESS to make it sound cooler or whatever, people say its black or white based on intention. This in an of itself is flawed. In asia and japan, The colors are flipped. White is a color of mourning and is often associated with death, where as black is noted to be the color of heaven and earth. So if you said you practiced "black" magick in older china or even a modern city, it can easily be confused.
Colors in the name are simply for esthetics. If theres one thing i think everyone can agree on, people who actually know what their doing arent obsessed with how something looks or sounds and instead works on improving their skills. Looks are trumped by efficiency and performance