01 -
Bring a large pot of salted water to a boil. Cook the rotini until al dente according to the package directions, then drain and rinse under cool water.
02 -
Divide the cooled pasta into three equal portions. Mix red food coloring with 1 tablespoon water in one bowl and blue food coloring with 1 tablespoon water in another, then toss one pasta portion in each color. Leave the third portion plain.
03 -
Drain off any extra coloring liquid. Toss the pasta with olive oil, spread it in shallow bowls or on a tray, and chill for at least 30 minutes.
04 -
In a large bowl, whisk mayonnaise, relish, lemon juice, dry mustard, kosher salt, and black pepper until smooth. Taste and adjust with more lemon or salt if needed.
05 -
Add the red, white, and blue pasta to the dressing with the chopped eggs, celery, and red onion. Fold gently until coated without breaking up the eggs too much.
06 -
Cover and refrigerate for at least 1 hour before serving. Stir gently, taste once more, and serve cold.