Question

WHY carbon is black colour?but diamond is white explaine

Answer 1

carbon is always black in colour......daimond is the polished form... moreover daimond is a allotrope.... so the differnce in properties is there

Answer 2

Carbon is not "black". Carbon is an element, and a single atom of carbon doesn't have color. 

Carbon bonds in different ways, and depending on how carbon bonds it will appear a different color, as these bonds will absorb and reflect light differently.