You can heat up the glue that holds the trackpad together and then remove the glass form the sensor. you would then need to 'scrape' away the silver colouring that is painted onto the underside of the glass. I am not sure how you would then go about colouring the glass before re-seating the sensor back against the glass. Also I do not know how sensitive this would then be after this process.
You need to be very carefull doing this as the glass shatters into very very fine splinters if bent too much.
Hope this helps,
Wes