What will the gray gene tell me?

Two of my horses have a gray mother. Neither one at this point are showing signs of graying out yet. If I was to have the test done at UC Davis for the gray gene, what is it going to tell me? Would it tell me that they will gray out for sure or not? Wondering if it's worth the money.

Yes, it will tell you if they are going to gray or not. If a horse is G/G or G/g, it carries the gray gene and, being a dominant gene, the horse will gray. If they came back g/g, they will not gray and it will also tell you that the mare is G/g.

Thank you!