DO NOT OPEN THAT PANEL IF YOU ARE NOT POSITIVE THAT YOU KNOW WHAT YOU ARE DOING!!!
I want to agree with JoeD, but a homeowner can be injured even kiled in an electrical panel. This is not a job for a novice. If a homeowner opens a panel and finds a black and a red on the breaker, what does he do? If he accidentally touches a wire, a main buss or a live breaker's terminal screws, what then?
The first thing You need to do is determine which breaker is providing power at the receptacle. Then determine if you can, whether anything else is on the same circuit. If so, stop and call an electrician. If not, then turn the breaker off and open the receptacle first. Check the color and orientation of the wire. If it's wired correctly, return it to it's box and cover it. If not, Call an electrician. Then when you or the electrician have good knowledge of what's in the receptacle box. The wire swap in the panel will be much more likely to be correct.
NEVER ASSUME THAT THE PREVIOUS ELECTRICIAN DOES EVERYTHING THE SAME WAY THAT YOU WOULD.
Code regulates us to certain parameters, but variables still exist that make a good understanding of electricity necessary to maintain our personal safety and the safety of others. I can't remember how many times I have been called to homes where the dryer or the oven was shocking people and found that the homeowners had wired a receptacle wrong, or an old receptacle was wired wrong.