It seems that I have overcolored my hair. It is nearly 100 percent gray beneath the color.
Right now it is jet black. I would like to return to strip my hair down to the gray. Is this possible or do I need to grow it out?

A trained hair stylist may be able to strip the color and use a blue and white toner to achieve the gray look. But this process is very tricky and can damage your hair. I think you should try to be patient and let your hair grow out naturally.