The Stretch Contrast, except that it works in the HSV color space, so it preserves the hue. It works on layers from RGB and Indexed images. If the image is Grayscale, the menu entry is insensitive and grayed out.
command increases the saturation range of the colors in the layer, without altering brightness or hue. It does this by converting the colors to HSV space, measuring the range of saturation values across the image, then stretching this range to be as large as possible, and finally converting the colors back to RGB. It is similar toFigure 15.96.  “Color Enhance” example (Original image)
The active layer and its Red, Green and Blue histograms before ΓÇ£Color EnhanceΓÇ¥.
Figure 15.97.  “Color Enhance” example (Image after the command)
The active layer and its Red, Green and Blue histograms after ΓÇ£Color EnhanceΓÇ¥. The result may not always be what you expect.