Boil your pasta according to its directions. Drain and rinse under water to get rid of excess starch. If serving later, lightly drizzle one tablespoon of olive oil onto your pasta to keep them from sticking together.
Add the pasta, tomatoes, cucumbers, bell peppers, and red onion into a large bowl. Keep in the refrigerator with plastic wrap until ready to serve cold. Gently toss with the vegan pesto sauce and serve immediately.
