For the Cajun Shrimp:
Heat a large skillet over medium heat. In a medium bowl, toss the shrimp with olive oil, Cajun seasoning, salt, and black pepper until coated.
Once the skillet is hot, add the shrimp and cook, stirring constantly, until they turn pink, about 4-6 minutes. Set aside.

For the Pasta:
Preheat oven to 350°F (177°C) and lightly butter a 9×13-inch baking dish.
Bring a large pot of salted water to a boil and cook the macaroni until al dente (follow package directions). Drain well and transfer to a large bowl. Mix in the Cajun shrimp, crab chunks, and basil. Set aside.

For the Cheese/Milk Mixture:
In a large bowl, whisk together whole milk and evaporated milk. Add paprika, cayenne, salt, and pepper. Taste and adjust seasoning as needed.
Add the beaten eggs and combine.
Set aside 1 cup sharp cheddar, ½ cup colby & Monterey Jack, and ½ cup Parmesan cheese. Add the remaining cheese to the milk mixture and stir to combine.

Assembly of the Mac and Cheese:
Pour the cheese mixture into the macaroni and stir to combine.
Transfer to the prepared baking dish and top with the reserved cheeses. Sprinkle with more basil, paprika, salt, pepper, and Cajun seasoning, if desired.
Bake for 45-55 minutes until the top is golden. Cover with foil around the 35-40 minute mark to prevent the cheese from touching the foil.
Remove from the oven and let sit for 25-30 minutes before serving.