1/2 pound red potatoes, diced 1/2 pound Yukon Gold potatoes, diced 1/4 pound purple potatoes, diced 2/3 cup black olives, halved 1/3 cup green onions, chopped 1/3 cup celery, diced 1 tablespoon red wine vinegar 2 teaspoons Dijon mustard 3 tablespoons extra virgin olive oil 1/2 teaspoon salt 1 pinch freshly ground black pepper 2 tablespoons flat-leaf parsley, chopped In large pot, boil water and potatoes. Cook until tender, drain and cool to room temperature. Combine potatoes, olives, green onions and celery in a large mixing bowl and set aside. In medium bowl, whisk together red wine vinegar and mustard. Gradually whisk in olive oil, then season with salt, pepper and parsley. Pour dressing over potato mixture and toss until evenly coated.