Fill a large pot with water, add salt, and bring to a boil. Add the green beans and cook for 4-5 minutes until crisp-tender. Drain and rinse under cold water.

In the same pot, add fresh water, bring back to a boil, add diced potatoes, and cook for 8-10 minutes until tender. Drain and let cool.

Add water back to the pot, bring to a boil, stir in tricolor pasta, and cook according to package instructions for 6-8 minutes. Drain and cool.

In a medium mixing bowl, whisk together lemon juice, minced garlic, olive oil, dried oregano, salt, and black pepper until well combined.

In a large mixing bowl, add halved cherry tomatoes, chopped basil, parsley, and drained tuna. Gently fold together.

Add blanched green beans, cooked potatoes, and cooled pasta to the bowl. Mix gently to combine.

Pour the dressing over the salad and toss gently to coat, being careful not to mash the tuna or tomatoes.

Serve immediately or chill in the refrigerator for 30 minutes before serving.