Wrapper discoloration, although not particularly pleasing to look at, doesn't affect a cigars taste, burn, etc., IMO. Some of the better cigars I have smoked have had discoloration..........and no, you cannot wipe it off. It's an intregal part of the leaf.
Mold on the other hand, as I've recently found out, can ruin the taste of a cigar. It can be difficult to tell the difference, but as a rule, if you can see mold on the outside of the cigar, whether it originated inside or not, you should be able to dislodge some of it. It will also have the characteristic "musty" odor, particularly if moistened. If you can't dislodge it, and you can't smell it when moistened, chances are it's discoloration, not mold. The caveat........."CHANCES ARE"...............I would segregate the cigar(s) any way, just to be on the safe side. Just my thoughts...............