There is incompletely filled d-orbital in Cu2+ ion of CuSO4 5H2O. Thus d-d transition of electron is possible in it. Hence CuSO4 . 5H2O is blue.
The d-orbital of Zn2+ (3d10) of ZnSO4 . 7H2O is completely filled. Thus no d-d- transition of electron is possible in ZnSO4. 7H2O . Hence ZnSO4 . 7H2O is colorless.