Depends, there’s good toning and bad toning. Natural (not induced by a chemical or artificial process) rainbow colored silver coins with red, blue, green, yellow ,and gold colors are highly sought after by collectors. Having the obverse of a coin toned will bring more premium when compared to the reverse. There is currently a very good market for rainbow toned coins in the Morgan Dollar space. Darkly toned brown and black coins will usually decrease the value of a coin. Once a coin tones black it’s pretty much irreversible, known in the hobby as terminal toning.
Does toning make a coin more valuable?
