Cook the Potatoes: Place the potatoes in a large pot and cover them with water. Reduce the heat and simmer for 10-15 minutes, or until the potatoes are tender but not falling apart. Drain and allow to cool slightly.
Prepare the Vegetables: While the potatoes are cooking, chop the red onions, green onions, parsley, dill, and olives. Set these aside.
Make the Vinaigrette: In a small bowl, whisk together the red wine vinegar, Dijon mustard, dried oregano, minced garlic, sea salt, and black pepper. Slowly drizzle in the olive oil while whisking, creating a smooth, emulsified dressing.
Assemble the Salad: Once the potatoes are cool enough to handle, cut them into halves or quarters depending on their size. Place the potatoes in a large bowl and add the chopped red onions, green onions, parsley, dill, and olives.
Dress the Salad: Pour the vinaigrette over the salad and toss gently until the potatoes and vegetables are evenly coated.
Serve or Chill: This salad can be served warm or at room temperature, but for a more intense flavor, let it chill for at least 30 minutes in the refrigerator before serving.