Understanding Premature Gray Hair: A Medical Perspective

Question
I hope you can help me with this question.  I have my few 7-9 white hairs at the age of 30.  I recently read on the internet that a black hair will turn orange, then to yellow, and then to grey.  Sort of like a slow process. I just wanted to know from a medical point of view if that is true, because i have various hairs in my head that are orangey/red tint, but I've always just thought that those are normal natural highlights in my dark black hair.  Makes me sad to think that all those hairs are saying that the'[re on their way to becoming white.  And I have a couple once in a while that are blondy.  Just wanted to know, like I said, if melanin is goes from having to not having, or if it really is a slow process of losing, causing a hair to change many colors before becoming white.  If you can't answer this, I would appreciate you directing me to a field that would!! but hope you can help!

Answer
There will be some that might change to funny colors but most just stop the pigment and start coming out white (or grey, or silver....)  For the individual hairs, the color change is pretty abrupt, however, hard to see the change when looking at the whole head of hair because of the multiple colored hairs around them......