Plain Greek yogurt will assume the flavor(s) of whatever you add to it. For a savory dipping sauce or condiment, consider fresh lemon juice and lemon zest, chopped fresh mint or tarragon, olive oil, heavy cream, sour cream, or a teaspoon of mayonnaise for added tanginess, chopped sweet or dill pickles, roasted and mashed garlic cloves, finely diced English cucumbers, minced capers, chopped fresh dill, or in the case of today's recipe, briny Kalamata olives.