In both of chromate (CrO42−) and dichromate (Cr2O72−) ions, Cr is present in +6 oxidation state, i.e. d0 -configuration. So, d−d transition is absent in both of the ions. Their intense colour (yellow of CrO42− and orange of Cr2O72−) is the charge transfer (ligand ⟶ metal) of oxygen get transfered into vacant d -orbital of Cr (VI).