Or (Conjunction)

Hello everyone! I have been having trouble understanding conjunctions, and how best to translate them from English to Japanese. I have seen many examples where a conjunction simply is removed and the two sentences are separated by question marks. Can anyone translate these sentences?

Who will arrive this evening, Nicholas or Natalie?
Do you like this one or that one?
Do you want the green one or the blue one?
Are you coming or staying?
Tell him the truth, or he'll hear it from me.
Did you tell him or not?

Thanks in advance!