The medical term for hair graying is canities. Hair turns gray (or white) when your hair follicles stop creating melanin. Melanin is the substance that gives your skin and hair color.
The coloring is very natural. I cut my hair very short on the sides and find that I have to color more often, about every two weeks, because the grays grow out longer than the dyed hair ...
No matter where you fall on the spectrum, one at-home hair color brand to know ... precision wand to target gray areas, then blend with the built-in comb for a natural finish.