Shine bright like vanadium! Vanadium can exist in four adjacent oxidation states (from 2⁺ to 5⁺). In aqueous solution, it forms metal aquo complexes. The color of these complexes depends on the oxidation state of vanadium: lilac [V(H₂O)₆]²⁺, green [V(H₂O)₆]³⁺, blue [VO(H₂O)₅]²⁺ and yellow VO³⁻. Ammonium vanadate (V) (NH₄VO₃) can be successively reduced with elemental zinc to obtain different colors of vanadium in these four oxidation states. Lower oxidation states occur in compounds such as V(CO