Prices for olive oil vary widely, but cost is not always a fair indicator of quality - sometimes it simply denotes rarity. Many good value olive oils are available from countries such as Spain and Greece at a third of the price of mediocre French and Italian olive oil.
The colour of olive oil, which ranges from pale gold to green, is usually more of an indication of the variety of olives used and their ripeness when picked than of quality or taste. The best green oils come from the first cold pressing of early-gathered fruit, but some manufactures now create the colour artificially by adding ground olive leaves to the olives during processing. Although most olive oils are clear, some unfiltered ones are cloudy and have small amounts of residue in the bottle; neither is harmful and the taste isn't affected.
Good olive oil is a condiment as well as a cooking medium.
Refined, ordinary olive oil and virgin oil are good for most types of cooking. Cold-pressed extra virgin oils lose some of their delicate flavour when exposed to direct heat, so are better sprinkled over lightly steamed vegetables, salads, soups, baked or boiled potatoes or pumpkin, grilled meats and fish, or serve in a bowl for dunking bread and crudités.
Fine or less expensive extra virgin oils make a good base for vinaigrette and pesto sauce.
Light is the enemy of oil. Always keep oils away from sunlight, and store them in a cool, dry cupboard.
Aim to use quickly, preferably within one year.