Why is Some Smoke Black While Other Smoke is Grey or White ?

The colour depends on what's in the smoke. When smoke is white it contains moisture. When it's black the smoke is carrying soot. And when it's grey the smoke has ashes in it. The colour of smoke depends on the composition of the smoke. White smoke contains moisture from damp fuel or hydrogen released as the fuel burns. Black smoke contains carbon particles produced by imperfect combustion. Grey smoke contains ash from poor-quality fuel. Sometimes white smoke looks blue because the blue component of sunlight is dispersed by the moisture in the smoke. Seen from a different angle however, the smoke will look white.