Question

why hydrated copper sulphate is blue in hydrated and white when dehydrated?

Answer 1

The common copper sulphate crystals you commonly see is CuSO4.5H2O which is hydrated in it's natural form,which creates the
blue colour while the unhydrated copper sulphate solution ,is obtained by dehydrating the copper sulphate crystals,is CuSO4. And also,we can observe that,When adding water to the unhydrated copper sulphate crystals it regains it's blue colour.