Blue should not be worn on stage.
The idea that blue should never be worn on stage is a superstition that not many thespians have heard. Perhaps this myth has not survived as strongly as some other superstitions because the reason behind it is no longer relevant. At one point in theater history, blue dye was the most expensive of all the fabric colorings. Producers, in an effort to discourage the spending of money on such luxuries, started a rumor that blue costumes were unlucky. Even then, the economics of theater were a dicey risk.