Coin toning is patina or simply put it’s oxidation that forms on coins. Oxidation can have an appearance in many variations of colors and shades. Usually different metal types may have different color formations. Gold, silver nickel, copper and other metals will have many of those variations.
Does toning effect the value of the coin? Beauty is in the eye of the beholder and since each toned coin is not like any other coin, it’s another layer of value to consider, along with grade, rarity, coin type, etc.