Green, blue, and purple metal compounds exist in various forms. Nickel complexes can produce green solutions, while copper sulfate yields a striking blue solution. Cobalt complexes also contribute to this color spectrum, with cobalt II chloride appearing blue when anhydrous and pink when hydrated, and cobalt II oxide being green. Potassium permanganate is noted for its purple hue. Additionally, nickel tetraammine complex (Ni(NH3)4++) is recognized for its violet color. Copper salts exhibit a range of colors, with anhydrous copper II nitrate and hydrated copper II sulfate being bright blue, while copper II chloride and carbonate can appear blue-green. The discussion highlights the importance of the anion in determining the color of copper compounds. For further exploration of metal compound colors, flame tests can provide additional insights into the visual characteristics of various metal ions.
