re: How fast can hair go grey?

I was blonde for about 50 of my 59 years. I started turning grey about 9 years ago and I am completely gray now....but its almost the same color was it has always been. My Dad have RAVEN black hair until my sister passed away and turned gray in about 6 months. My mom was the same except she was blonde. Its probably tougher on folks with darker hair....mine has always been almost white, especially in the summer, so it being gray is not as big a shock....