I love when they get those white ring on their eyesGood question.
Grey horses are not born grey. They are born what their base color would be. Bay, black, red, palomino, ect. They are also born hyperpigmented. This means if they are black based, they are born jet black instead of the mousy grey color that a true black is. Most, not all I think though have another tell tale sign, they are born with grey goggles around their eyes. By their first foal shed you will start seeing the lighter grey hairs show up in their coat. Grey is a fascinating gene in truth. Some horses grey extremely fast, by 2 or 3 they are a light grey and white before 10. Some grey slow and stay darker and dappled into their teens. Eventually though they will all end up that iconic flea bitten grey almost white horse if they live long enough.

I was really hoping Truly would stay chestnut, I checked for white hairs around her eyes every day when she was born, then at 10’days old the white hairs started sprouting - I was so upset, grey/white horses are so labour intensive when showing.