In a large mixing bowl, combine black beans corn, red bell pepper, green bell pepper, red onion and cilantro.
In a separate bowl, mix sour cream, yogurt, vinegar, cumin, chili powder, salt, pepper and garlic powder until well combined.
Pour yogurt mixture over corn mixture and toss gently to coat. Store, covered, in refrigerator before and after serving.
Serve with chips or crackers (not included in nutrition information).