Gray, or white, is merely the base color of our hair.
Pigment cells located at the base of each hair follicle produce the natural dominant color of our youth.
However, as a person grows older and reaches middle age, more and more of these pigment cells die and color is lost from individual hairs.
The result is that a person’s hair gradually begins to show more and more gray.
The whole process may take between 10 and 20 years, rarely does a person’s entire collection of individual hairs, which, depending on hair loss, can number in the hundreds of thousands, go gray overnight.
Interestingly, the color-enhancing cells often speed up pigment production as we age, so hair sometimes darkens temporarily before the pigment cells die.