Plain yogurt and grainy mustard make a light, tangy sauce for potato salad. Serve slightly warm or chilled.
1. Place potatoes in large saucepan, and cover with cold water. Bring to a boil. Reduce heat to medium, and cook 5 to 6 minutes, or until potatoes are tender, but not soft.
2. Meanwhile, whisk together yogurt, mustard, and olive oil in large bowl. Stir in red bell pepper, celery, and onion.
3. Drain potatoes, rinse under cold water, and drain again. Add potatoes to yogurt mixture, stirring to coat. Season with salt and pepper, if desired.