Zn salts are white while Cu2+ salts are coloured. WHY?
Zn has electronic configuration = 3d104s2
Zn2+ = 3d10
Cu = 3d54s1
Cu2+ = 3d4
In case of Zn fully filled d orbital is present therefore no d-d transition can be possible in this case and it is colorless.
In case of copper because of d-d transition electrons emits light in the visible range and hence they are colored compounds.