Go to the nearest drugstore and buy the blue ones (they're the ones that are shaped like bullets and made from foam, not the kind that are made from plastic/wax or whatever). The purple ones are not as good as the blue ones, IMO, but both will work okay. The pink ones aren't that great, but they sometimes come bundled with a pink sleep mask which is awesome (the mask, that is, it's excellent). You'll want to get a lot of the blue ones because if you use them on a nightly basis, you'll lose them/run out.
* I have no idea what the brands are, sorry.