Rinse quinoa under cold water to remove bitterness.
Cook quinoa: In a medium pot, bring 2 cups water and quinoa to a boil. Lower heat, cover, and simmer for 15 minutes. Remove from heat and let sit covered for 5 minutes. Fluff with a fork.
Prepare vegetables: Dice mango, bell pepper, and onion. Chop cilantro. Blanch green beans in boiling water for 2 minutes, then transfer to cold water and drain.
Mix vinaigrette: In a small bowl, whisk lime juice, olive oil, honey, garlic, salt, and pepper.
Combine salad: In a large bowl, add cooked quinoa, black beans, mango, green beans, bell pepper, onion, and cilantro. Pour vinaigrette over and toss gently.
Rest & serve: Let the salad sit for 15–20 minutes so the flavors blend. Serve chilled or at room temperature.
