In response to that stallion having some grey hairs, there was another horse on the page I posted, a mare, who does not.
I apologize for not being able to get the larger versions, I think the link died. But that is a palomino, no grey hairs. With the first one, he was golden for much longer. This mare, as documented below, went dark VERY fast, and since we don't know how the sooty gene works really, that may have something to do with it.
That is the mare at birth. Normal, right?
As a yearling. Not as normal.
As a two year old, she looked more palomino, but darkened quickly, as shown.
Just goes to show, you really can't judge a horse a palomino or not unless you owned them from birth or color test them haha.
But the point is, that mare does not have the greys interspersed.
I wish I had saved the large version of those pictures before the links broke, you can see it better.