Grey is a modifier gene I believe. All greys are born as the color they would be if they did not have the grey gene. They can be any color but if they also carry the grey gene then as they age their coat color fades out. Depending on the horse some grey fast and can be almost white in a few years while others grey slowly and be in their teens and still not be white. Another interesting fact is that at least 1 parent has to be grey for the foal to be grey. Does not matter if all 4 grandparents are grey, if neither parent is grey the foal will not be.
