Hue is a transparency type in the Transparency Tool. It is useful for color-shifting underlying objects. Its action is most easily understood using the HSV color model.

The color of the object with Hue applied:

Gray, White, & Black - has no effect. These colors lie at the center of the color wheel and so have no hue.

If the underlying color is gray, white, or black - Hue transparency type has no effect.

Other colors - replace the Hue of the underlying color with the Hue of this object. Use the Saturation and Value of the underlying color.