The Schneider 4x4" Combination Color Conversion 85/ND 0.6 Glass Filter will produce natural colors when shooting with tungsten film outdoors. Using tungsten film in daylight will produce a bluish cast in the photograph. 

Neutral Density filters have several uses and offer the possibility to achieve otherwise unachievable results. ND filters appear grey and reduce the amount of light reaching the film. They have no effect on color balance.