There are a few factors that vary the flavor of true olive oil. Factors include the type of olive, the process used, are the olives ripe or green, etc. Not matter the factors, the olive oil should taste fresh and only the actual flavor should change. Some of the flavors you could experience are peppery, sweetness, spicy or fruity. and sometimes even a little bitter. If you have ever noticed that some olive oils have different shades, that is also due to the olive used. Green olives tend to be lighter in flavor and may even have a greenish color while riper olives will give off a darker yellow and even a little buttery and rich. The trick is to make sure that you are buying true olive oil.
Another note is just because an olive oil is labeled extra-light, or light, does not mean quality or less fat, it usually means that it may be of lesser quality. Try to buy your olive oils from smaller producers that package their oils in darker or metal bottles. Since it’s important the way you store your olive oil and keeping it away from light, it’s great to know that you are purchasing it like that to start.
Check out these sites/article for more information on many other Olive Oils: The Worlds Best Olive Oils , The Best and Worst Olive Oil from the Grocery Store