In comparison with boxing, that has adopted a range of colors either for color psychology or marketing or fighters' visibility and reaction, why are the UFC gloves black? Does that color shortens in any way a fighter's potential reaction time?
Because racism.
what do you want them to be, the colors of the rainbow?
who gives a shit what color they are
they're black AND white.
You could also argue that they don't want anything taking focus away from the actual fighter. Colorful gear etc might draw attention to the gear instead of the fighter.The same reason why the UFC has forced the fighters to wear uniforms. They don't want anything to distract from their own company brand. A variety of colored gloves, customized fight gear would put more focus on the fighters and the UFC can't have that.