Gray is a gene that lightens any color over time. Your horse may pass this onto their foal if they have one copy of the gene (Gg) if they have two copies (GG) the foals will all turn gray.

You can get a gene test at the vet to check your horse. 

More info about gray can be found here: https://en.wikipedia.org/wiki/Gray_horse 

you can also read about how grey specifically works on HoFa here and here, it's a bit different from how greying is in real life.

thank you so much!😊