Best you can do is
image >> mode >> indexed >> OK
image >> mode >> color table >> save
This has been useful to me in the past, so thought you may have a need for
You can then load this color table into a new image. You are limited to 256 colors. It soudns like you are looking for a data list showing each of the colors used in an image and their individual cmyk or rgb breakdown. There is no way to do this except using the info palette and manullay writing down each pixels value by hand.
Do you really need the colors of all the pixels or just a few of them?