So what really happens is when you notice a grey hair?

You pull it out, right! The action of pulling out the hair may rupture the hair follicle, and the replacement hair that eventually grows in will take longer to regenerate. Then another grey hair will begin to grow next to it. When the hair that was originally pulled out grows back, you have two grey hairs. I hear all the time that people feel like they have to pull out the grey hairs they see. Some people say that they will not do that again. Then others will just keep on pulling the grey hairs out. Oh well!