What makes hair go gray? Can you go gray suddenly if you’re sick or upset?

In young people, hair gets its characteristic blond, brown or black color from varying amounts of a pigment called melanin, the same pigment that colors skin. But with normal aging, hair follicles produce less and less melanin, allowing the underlying white color of hair to become apparent. A head of hair looks gray when some hair has turned white and the rest is still pigmented.