The colour of anhydrous copper sulphate is

Blue is the colour of hydrated copper sulphate, ${\mathrm{CuSO}}_4\cdot 5{\mathrm{H}}_2\mathrm{O}$. The splitting of d orbitals is caused by the ligand (water) molecules. This makes the colour and d-d transition easier.
${\mathrm{CuSO}}_4$, anhydrous copper sulphate, has no colour. Splitting of the d orbitals is not conceivable in the absence of the ligand (water) molecules. D-d transition is therefore not achievable.