Transition metal salts. Transition metal salts are often colored. Photographed here, left to right, front row, solids: potassium chromate(VI) (K2CrO4, yellow, in a vial), copper(II) carbonate (CuCO3, blue-green, in an evaporation dish), nickel(II) sulfate hexahydrate (NiSO4 6H2O, green-blue, in a beaker); copper(II) sulfate pentahydrate (CuSO4 5H2O, blue, in a beaker); back row, solutions: potassium permanganate (KMnO4, in an Erlenmeyer flask), ammonium metavanadate(V) (NH4VO3, in flat-bottom boiling flask), potassium dichromate(VI) (K2Cr2O7, in a volumetric flask), iron(III) chloride (FeCl3, in a reagent bottle).