Recently I replaced all of my outlets and some of my switches in my apartment. On many of them, I used masking tape or painter's tape exclusively to identify wires (but never as insulation). I left the tape on the wires on the newly installed outlets and switches. Is this dangerous? Should I open up all my outlets and switches to remove all this tape?
Given what you said in your comment about the tape being like label tags, I'd kill power, pull the cover plates, and reach in with an needlenose plier or surgical clamp (fishing hook remover) and yank out the loose ends. They should tear free without disturbing your wiring.
This will dramatically reduce fire hazard (what little there is), and would meet my personal standards for safety. As Ecnerwal mentioned, it's probably a code violation, but....
Electrical tape would be fine. You can get it in many colors, too.
Masking/painter's tape does add some risk, as it's not got the same rated performance in overheating/fire conditions and might ignite or serve as a fuel source. It's a small concern, but it's a concern, and very probably a code violation.