Put 1 pound each chopped blue potatoes and white potatoes and 1/2 pound chopped red potatoes in a large pot. Cover with cold water; add 2 tablespoons white wine vinegargarlic and a pinch of salt. Bring to a boil, then simmer until the potatoes are tender, about 15 minutes. Drain and cool slightly (discard the garlic). Toss with 1 1/2 cups halved cherry tomatoes, 1/3 cup torn basil and 2 tablespoons each chopped scallions and parsley. Dress with 1/4 cup olive oil, 2 more tablespoons vinegar, and salt and pepper.