Onions, leeks, scallions...

At the moment i'm using only red onions/garlic in my green salad. I tried yellow ones, but i don't like them. Has anyone tried using the following raw foods in a salad: white onions, leeks, scallions, pearl onions (red & white). I noticed all of these at the grocery store, but i never used them. Can anyone tell me what each of these is used for, which ones can be used raw, and which ones are good in green salads.