It indicates nothing. I have substantial hair loss and little discoloration. An older friend of mine has minimal discoloration and no hair loss at age 70. Three people I know, two brothers and, oddly enough, their brother-in-law (no blood relation and no ancestral geographic connection besides Har Sinai), have full heads of white hair and all went grey in their 20’s.
Stress is not a factor. Neither is weather; one of the 2 brothers moved from a warm climate to a very cold one (and that is what I thought caused his premature greyness), but the other moved from a warm climate to a downright hot climate. The third grew up in and remains in a colder climate. The older man went through the war and the Communists and lived in many places. He had a very stressful life and still does as an askan. I also moved from a warmer climate to a colder one.