I have a grey arabian mare, who's mom is a flea bitten at 13 years of age, and who's dad is a bay. She at 4 years old had an almost flea bitten looking head, is definitely lighter than the body, but the legs and mane are completely black still, as is most of her tail. Her mom retained a pretty dark mane and tail herself. My horse's coat is also very very dark still, though I know that in a few years she will be lighter. It is very true that the lightening process differs in horses. I know a horse that a year ago looked very similar to my mare, but now is almost completely "white". It is a bummer in one sense that they lighten out as they age, but at the same time, it makes for a more interesting horse, to look back at pictures over the years, and see the horse when it was very dark, and watch as it has lightened up. I've read in a color genetics book that you can generally tell relatively accurately how quickly a grey is going to lighten up. The head mane, tail, and legs are generally the first to get light, and as soon as those lighten up, the body starts lightening up quicker. But we shall see with my horse, as it also said that generally by the time a grey is 3, it should have a considerably lighter head, and by the time its 4 or 5 should be getting lighter in the body, and my horse at almost 5 has a light head, but still dark mane, mostly dark tail, black legs, and a very dark body. She does have black skin though, as that had to be recorded when her papers were being drawn up, though I'm not exactly certain what difference that makes whether the horse has pink skin or black skin. If anyone knows, I'm definitely curious about it.