salts are white while salts are colored. Why?

The electronic configuration of Zn is while the EC of Zinc ion () is or . While the electronic configuration of Copper is and the EC of is . In the case of Zinc, the d orbitals are completely filled therefore, there is no d-d transition so, no color is imparted. On the other hand, Copper has incomplete d orbitals which lead to d-d transition which results in the formation of colored compounds or salts.