Combine all of the ingredients in a jar and shake vigorously to combine. Store in the refrigerator until ready to use.
For the salad:
Cook the spaghetti in salted water according to package directions. Drain and rinse under cool water.
Place the spaghetti in a large bowl and add the cucumber, red and green bell pepper, cherry tomatoes, red onion and olives. Pour the dressing over the pasta and vegetables and toss to coat. Season with salt and pepper to taste if desired. Sprinkle the parmesan cheese and parsley over the top right before serving. Salad can be made up to 4 hours in advance.