Step 1

Heat vinegar, sugar, oil, garlic, salt, and pepper to taste in small nonreactive saucepan over medium heat, stirring occasionally, until sugar dissolves, about 5 minutes. Transfer to a large nonreactive bowl and cool to room temperature.

Step 2

Bring 3 quarts water to boil in large saucepan over high heat. Add 1 tablespoon salt and green and yellow beans; cook until crisp-tender, about 5 minutes. Meanwhile, fill medium bowl with ice water. When beans are done, drain and immediately plunge into ice water to stop cooking process; let sit until chilled, about 2 minutes. Drain well.

Step 3

Add green and yellow beans, kidney beans, onion, and parsley to vinegar mixture; toss well to coat. Cover and refrigerate overnight to let flavors meld. Let stand at room temperature 30 minutes before serving. (Salad can be covered and refrigerated up to 4 days.)