Bring water and a pinch of salt to a boil in a saucepan. Add quinoa to water, reduce heat to medium-low, cover, and simmer until quinoa is tender and water has been absorbed, about 15 minutes. Cool.
Stir cooled quinoa, tomato, carrot, green onion, mint, and parsley together in a bowl.
Whisk lemon juice, olive oil, 1/2 teaspoon salt, and ground pepper together in a small bowl until dressing is smooth. Pour dressing over quinoa mixture and toss to coat. Cover the bowl with plastic wrap and refrigerate until flavors combine, about 30 minutes.