Each Toned coin has it's merits with the quality and eye appeal varies from coin to coin. It can also be a Toning in progress and may not necessarily stop until its sealed away from air, starting out as a light golden may end up a much darker one in a few years later depending how much free Sulphur ions are in the air.
If you want to prevent toning some Numismatists store copper coins with the silver ones as Copper has a higher reactance than silver.