It's toning. Toning isn't a variety, it's a chemical reaction with other substances reacting with the metal the coin is made of. Coins can turn many different colors and can sometimes add value if it's attractive (beauty is in the eye of the beholder). Here's a toned cent in my collection:
Red, Red-Brown, and Brown are simply what percentage of the coin is a color (original or not original color). Red means that more than 95 percent of the area of the coin retains it's original red coloring, Brown means that less than 5 percent of the coin is still the original red, and Red-Brown is all the other in between. Start learning to imagine in your mind when you see a cent coin, how much of the coin equals 5 percent. It's one way to start figuring out which ones are Red and which don't get to that amount. Toning is not included in this, I don't believe. But I could be wrong on this. Perhaps someone else will answer.
