This plugin creates a hue gradient and shift effect from the vector length of an image's RGB value.
This is a classic effect, as commonly used in poster art from the 60's and 70's.
A small HueMultiply value will create a small gradient shift, like would commonly be scene in the previously mentioned poster art, or similar to the light art of James Turrell. Large HueMultiply values will cause rainbow type effects.
HueShift will offset the starting point of the hue gradient rotation effect.
Saturation and Lightness are, hopefully, self explanatory.