The accurate humor settling technology used for Hoya Pro ND filters results in a neutral color balance that does not cause any noticeable discoloration in the images. So you can adjust the white balance once and be sure that you will get the same color balance if you need to change a filter, or the illumination changes or even for the creative effect.

This ND filter also has the same weakening effect on infrared rays that cause otherwise discoloration as the visible range.
Their latter property makes the color balance of Pro ND filters even more neutral.

The goal of designing neutral density filters was to reduce only the amount of light entering the objective, while no other effect on the image. And reducing light intensity also allows you to choose wider bleach or even longer locks to achieve the desired creative or dramatic effect.