What part of a compound is mostly responsible for the colour?

Question

The metal or the nonmetal?

Sorry Which part of the compound is mostly responsible for the colour "Produced by the flame".

Answer 1

It is usually the metal. The metal responsible for the color can be the cation, like Cu+2 in blue CuSO4, or it can be in the anion, like CrO4= in yellow Na2CrO4. Sulfur is a nonmetal, but its presence in compounds intensifies the color. CuS is an opaque dark brown. The nonmetallic ion thiocyanate, CNS-, reacts with yellow ferric [iron(III)] ion to form a brilliant red complex.

Additional detail: The metal, of course!

Answer 2

The color (American spelling) of any substance is dependent on the wavelengths of light that it absorbs. You probably knew that. If the compound is an ionic substance, particularly a transition metal salt, we ordinarily attribute the color to the transition metal ion itself, generally complexed or bound to some kind of ligand, like water. Often a compound that is white (reflects all colors and absorbs none) while anhydrous, is some color when hydrated. That's why copper II salts are typically blue or blue green in water, or when hydrated in crystalline form.