What color does pH paper turn when dipped in ammonia?

Unfortunately, it depends on the type of pH paper. If you mean standard litmus paper, it will be red (red litmus paper stays that way and blue litmus paper will turn red). Universal indicators change multiple colors depending on pH. If you have dilute concentrations of the same acid you will actually get different colors since pH indicates how much acid is dissociated, not how strong the acid is. Many universal pH indicators turn green colors at low pH.