While some might think that all green beans are the same, there are actually many different varieties, each with its own unique flavor profile.  Common green beans have a crisp and slightly grassy flavor, while Romano beans are nutty and earthy. As a result, the best spices for green beans will vary depending on the bean you use.  For instance, garlic and onion are classic choices that can help to enhance the flavor of almost any dish. Try red pepper flakes or cayenne pepper if you want to add a bit of heat.  Or, for a touch of sweetness, cinnamon or nutmeg can be used.