Like the previous posters have already mentioned, getting white hair is due to genetics.
Sometimes stress and anxiety can trigger it off.
If you are talking about yourself, your profile says you are 40 and at that age you can expect to have some white hair. My female friend's hair was white at that age. I have also seen a young woman with completely grey hair. All down to genetics!
I will be 61 this year and I still have a lot of my natural colour with a few white ones, but it has gone lighter on the top through the years. My colour is a chestnut brown and very thick - and long.
My brother and I started turning gray in our teens. The man I married started turning gray in his twenties. All of our four children grayed early. Blame heredity. We are all healthy and eat well.
Hi and wecome, what if learned and experienced myself, hair color is genetic. They say most about hair loss is inherited from your mothers dads genes and the actual color more from your dads. If your experiencing this genetically just pull them out if there one or two but, dye them when they accumulate more and eventually let it all go white.
There are however certain conditions that affect the loss of color other than genes but not knowing you it would be a guess only.