Colour of KMnO4,K2CrO4,K2Cr2O7 is due to

The number of unpaired electron in KMn+7O4,K2Cr+6O4,K2Cr+62O7 respectively are 0,0,0.Un paired electron are not available,hence they should be colour less,but they exhibit colour property due to charge transfer between ligands and central metal.