In my experience, it's easy to determine if the orange wire is 480 or the high leg of a 240 delta. Just look at the other wires it's with. Around here (Reno), 277/480 is brown, orange, yellow, and gray. 120/240 delta is black, orange, blue, and white. You can't have one ungrounded conductor by itself, so the other wires it's with will determine the system.
The only confusing scenario I can think of would be orange and white. Is it the 240 high leg and neutral, or 277 and the installer ran out of gray? Never seen the former, but have seen the latter.