Concept:Transition metals often show variable oxidation states, which can produce brightly colored compounds.Explanation:Copper is a transition metal that commonly exists in the +1 and +2 oxidation states.This variety causes its compounds to appear in many colors, especially blue and green.These colored copper compounds are widely used in pigments and paints.For example, CuCO3 and related copper complexes provide green and blue shades.Silver and gold are less colorful, while zinc normally shows only one main oxidation state.Answer:B. Copper (Cu)