Adjusts the image’s colors using the HSV method. Other transformations can also affect color, such as Grayscale and Max Colors. If you are using more than one, consider the order to apply them for the desired results. Hue/Saturation/Value is identical to Hue/Saturation/Lightness except it replaces the lightness with a value. An example of the difference between lightness and value is, given a very light green (almost white) as input, reducing the lightness produces a vibrant green (closer to pure green), whereas reducing the value produces darker colors, close to gray in this case as the input color was very close to white.
If you add the IMQuery transformation to a policy, use the im variable, and select Hue/Saturation/Value, you can use a query string to adjust the colors of any image using this policy. See Syntax and Examples for the syntax for the query string parameter.