Question

what is that thing that all human have black colour

Answer 1

What makes black people's skin dark?The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans.

Answer 2

human skin produces melanin which gives a dark appearance.