Bring 2 1/2 quarts water to a boil; add shrimp, and cook 3 to 5 minutes or just until shrimp turn pink. Drain; rinse with cold water. Peel shrimp, and devein, if desired.
Cut bell peppers and onions into strips. Place in a zip-top plastic bag; add shrimp. Combine vinegar and next 5 ingredients; pour over shrimp mixture. Seal bag, and chill 8 hours, turning occasionally.