Fuel injectors?

Hello, you are referring to the lower injector seals, yes there is an upper and lower, the upper is usually a rubber o-ring type. put a little bit of clean engine oil on the seals before installation. The lower ones seal the injector to the cylinder head. If you are doing the upper seals do the lower ones as well. In service information it looks like the lower seals are green. That might be the OEM seals' color. Once the seals are in and the fuel rail is back on, prime the fuel pump a few times by turning the key to the on position but don't start it. Prime it at least 3 times and check for leaks first.

Were you having misfire codes? Any check engine light on?

https://www.2carpros.com/articles/how-to-replace-a-fuel-injector

Yes all the seals are necessary, without the nylon seal the upper o ring will not stay in place while installing the fuel injectors, a lot of vehicles have a nylon seal on the bottom of the injector, but when pushing the injector into the intake manifold, with new seals they can be tough, but the upper o ring and then the nylon seal will prevent any fuel from leaking out of the fuel rail at the top of the fuel injector. Without it there will be fuel leaking onto the hot engine.