It would be best to watch his video to see the theory behind how he puts it together. I'll summarize below the ingredients - and here is a link if you have time to watch his whole video. He's not my favorite YouTube cook - because he is old-school - but if you are hungry for old-school, he's pretty good.
https://foodwishes.blogspot.com/2015/06/classic-macaroni-salad-delicious-is-in.html
Ingredients for 12 portions:
1 pound (4 cups) uncooked elbow macaroni, cooked in well-salted water
For the dressing:
1 cup mayonnaise, plus an extra spoon as needed
1/4 cup white vinegar
1 or 2 tbsp white sugar
2 tablespoons Dijon mustard
2 tsp kosher salt, plus more to taste
1/2 teaspoon ground black pepper
1/8 tsp cayenne
1/2 cup green onions, white and light parts
1 cup finely diced celery
3/4 cup diced red bell pepper (Jean did not add either red or green pepper - and went with pepperoni and cheese instead - see below)
1/2 cup diced green pepper (I used poblano and jalapeno) <that is the in the original recipe
1/2 cup grated carrot
My abbreviated instructions - his directions have all the *why* behind the directions:
Make the dressing first and add the vegetables - and put in the fridge so they have a chance to *pickle* a little bit while you cook the pasta.
Boil the pasta as directed and DO NOT undercook it.
Drain it and DO NOT rinse it.
Let it come to room temp - and it will be sticky - so toss it around a little.
Room temp and sticky helps the dressing to cling to the pasta.
After combining the room temp pasta and veggies in dressing - it may seem too loose - but that's as it should be because you let the pasta absorb the dressing OVERNIGHT in the fridge.
Before serving - adjust the seasoning - and add more mayo or water if it needs to be a little looser. Personally, I would consider adding a little olive oil at this point - it just depends on what kind of dressing you like on your pasta salad.
This is a good base for any kind of pasta salad. As mentioned above, I add diced pepperoni or salami with cheese and olives.
Other options I like are chicken and cheese or ham and cheese - and none of the chopped peppers with these options.