Place the baby potatoes in large pot with salted cold water covering the potatoes by 1 inch. Bring to boil over high heat, reduce heat to medium-low, and simmer until potatoes are tender, about 10 to 15 minutes.
Drain potatoes thoroughly, then add them back into the hot pot to dry completely. Drizzle the vinegar over the warm potatoes and toss gently until evenly coated.
Transfer the dressed potatoes to a large bowl. Cover the bowl and refrigerate until cold, about 30 minutes.
In a separate bowl, whisk together the yogurt, mayonnaise, and mustard until smooth and even.
Add mayonnaise mixture, celery, green onion and olives. Gently stir until evenly incorporated.