Red onions come in many varieties. They are not only used to add flavor but to add color to various dishes as well. 

The white onion is a popular cooking onion. It is often used in herbed, spicy dishes because of its clean, tangy flavor. Because white onions have a slightly higher water content, they are somewhat sweeter than yellow onions.

Sweet onions have a thiner, lighter color skin than storage onions and tend to be more fragile. Signs in product sections usually differentiate between sweet onions and yellow onions.

When you are looking for an onion to put into a cooked dish, the yellow storage onion is typically what most people will buy. It is usually available year round.