In color psychology, black means power and control, hanging on to information and things rather than giving out to others.
Black is intimidating, unfriendly and unapproachable because of the power it exudes.
It can prevent two-way communication because of its intimidation. The salesman wearing all black will make a lot of sales, but no friends! It radiates authority, but creates fear in the process.
Black implies self-control and discipline, independence and a strong will, and giving an impression of authority and power.
Black absorbs negative energy. It is useful to carry something black with you to protect you from harm and negativity when traveling or when going about your usual daily activities outside your home.