- Cook pasta according to package directions.
- Drain; cool.
- In a large bowl stir together yogurt, mustard, and herb seasoning.
- In another bowl take cooked shrimps, pasta, celery and green onions and mix well
- Add in the yogurt mustard mixture over pasta and toss.
- Chill at least 2 hours.
- Just before serving, carefully stir in tomatoes.