I am not a programmer, but it appears to affect massive rendering of color definition in objects. Hence, in my system without it things are slightly more muddy.
-noshaders
Disables Pixel and/or Vertic? Shader's (part of Direct X). Using this with the dx8 switch may help you get GW to run better (less taxing on the card) for low end cards / not quite supported (on board intel for example).