Hi Sparco and thank you for your very good questions.

The pads work by stimulating the body to release, through various channels, kidney one in particular but not exclusively (please refer to a foot meridian chart). The pad also generates an increase heat and blood flow into the area. Finally, the pad creates a "negative ion" effect, which is an osmotic shift that allows for the exchange from the inside of the body to the pad.
The moisture along with the toxins and a certain amount of sodium will cause the pad to change colors. Some people will notice changes in the color spotting or hue after continuous use, reflecting the changes in the toxins released.
Tourmaline will darken the pads just by the nature of it innate color. However, the other properties of tourmaline give additional harmony and energy flow to the herbal formula in the pad.
The increased energy many people feel after using the pads is due to the pads ability to improve blood flow and the "relief" from the detoxification.

Best Wishes,

Dr Vinograd