Only man grows vertically. Instead of growing horizontally, it is God's will that he should grow vertically in order to look up. He has given intelligence. When any object is consumed by fire, it becomes charred. If that black residue is burnt again, it becomes white ash.
White ash continues to remain white even when burnt again.
This shows that white is the ultimate and black is proximate to it. Science tells us that diamond and coal are basically one. White and black are not colours. The primary colours get separated from the objects to which they are attached when subjected to the test of fire and ultimately white. Similarly, in the mental and spiritual place, the Ultimate Reality is Siva, who is white and proximate to Him is Parvati, who is dark.