In a small bowl, mix together tuna, mayonnaise, Dijon mustard, lemon juice, and salt and pepper to taste. Stir in carrots, red bell peppers, and celery. Place 6 torn leaves of romaine lettuce on half of the slices of Country Double Fiber Bread. Spoon tuna mixture on top of the lettuce slices. Place another torn lettuce slice on each tuna sandwich and cover with another slice of Country Double Fiber Bread. Wrap sandwiches in colorful plastic wrap or wax paper and keep chilled. Your sandwiches are now picnic ready!