Color image segmentation for colors with same HUE, but different value and saturation

I have a color image in which the foreground has three shades of green(same hue, but different value and saturation). The background is black. I need to segment it. The segmentation method shouldnt be interactive as it is intended to work on many images at one go.The image has been generated by rotating a 3D model around a point source of light. The source 3D model has 3 regions with 3 uniform shades of green. The illumination variation changes the appearance(saturation, value) of the shades.

The sample images along with manually segmentations are attached herewith. Within each segmented region the "saturation" and "value" are not constant but slowly varying due to lighting effects. The hue is constant for the entire foreground.