Farb is a derogatory term used in the hobby of historical reenacting in reference to participants who exhibit indifference to historical authenticity, either from a material-cultural standpoint or in action. It can also refer to the inauthentic materials used by those reenactors.
Also called "polyester soldiers,"[1] farbs are reenactors who spend relatively little of their time or money maintaining authenticity with regard to uniforms, accessories, objects or period behavior. The 'Good Enough' attitude is pervasive among farbs, although even casual observers may be able to point out flaws.
Farbiness is dependent upon context as well as expectations and is somewhat subjective. For example, while a "mainstream" reenactor might accept an object that looks right from a spectator perspective, a "progressive" or "hard core" reenactor might consider the object to be farb if it's not made in a historically accurate manner.
http://en.wikipedia.org/wiki/Farb_(reenactment)