This filter is designed to compensate the hue shift in overexposed images, a phenomenon which occurs due to color clipping in RGB space. Overexposed areas often suffer a hue shift towards yellow, cyan or magenta, whichever is closest to the original hue. For example, skin tones turn yellowish when the flash was too close to the model. This is because the red channel - the dominant color in skin tones - is clipped resulting in too much green and, to a lesser extent, blue in proportion. Likewise the sky in otherwise correctly exposed images sometimes may look greener than in reality. In this case it is the blue channel which is clipped, leaving too much green.
Hue Restorer will find overexposed areas in an image and let you choose the hue to be restored. Correctly exposed regions will not be altered. Easy-to-use presets are available for restoration of skin tone and blue sky, respectively.