The onion which is also known as the bulb onion,common onionis the most widely cultivated species of the genus. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, Onions are often chopped and used as an ingredient in various hearty warm dishes, and May also used as a main ingredient in their own Dishes. Common onions are normally available in three colors: yellow, red, and white. Yellow onions, also called brown onions, are full-flavored and are a reliable standby for cooking almost anything. in sri lanka mostly you find brown onion. And our onion is so strong in flavor.