His winter coat will grow in that yellow color as well, this is why I don't really think it is faded. I know he is rinsed after every ride so he does not sit in the sun with sweat ever but I know sunburns on people can happen very quickly so it is a possibility. I would like him to be more brown because the yellow is odd to me but he's my daughters baby and she thinks he is always perfect. The summer we bought him he was very black and he was in a field with almost no shade the entire summer and had not faded a bit, maybe it's an age thing.
It's probably more the sweat from being worked. How old was he when you got him and was he being worked regularly then? If that's really the only difference, then that is more than likely what is causing it.
We had sun today so I was able to get a better picture. He was two when I got him but I don't know how much he was being worked. He is with a trainer and is worked almost daily so it could be sweat bleaching him which is what I had thought except that his winter coat comes in this color as well, even lighter last winter. We did pull some mane to send in just for fun. Thank you everyone who has given their thoughts.
With a sun-bleached coat you will still have the sun-bleached look in winter too, at least my horse did. In Spring/early summer when her new hair/coat came in, it was much darker because it hadn't yet gotten sun-bleached.
One thing to think about. If a horse is worked outside almost daily (or turned out daily), and are prone to fading, the hair will fade almost as quickly as it grows in, so they may never be "black". It's worse if they are in training/work because the sweat makes the fading worse, even if you rinse them off after every ride.
I could be completely off, here, but I thought I'd share this and see if it applies at all.
My 6 year old, Stormy, is supposed to be a smoky (smokey?) black. His mom was a bay, no idea on Dad.
When I lived in Tennessee, he was pasture kept. His summer coat was horrible, a streaky brown that looked faded. He'd get considerably darker in the winter.
I moved to Phx, Arizona about 3 years ago. Since then, he is in considerably stronger sun, in constant turn out with a shade structure that he uses on and off. What changed dramatically was his diet - he was on a fescue pasture with a general supplement and alfalfa pellets there. Here, he's on alfalfa/ bermuda hay, the same supplement and pellets. He is nearly jet black all year round (taken today, although he's just been put back on a little Alfalfa after losing some poundage and looks just a touch browner than usual)
So, for my smoky black, sun doesn't seem to be the big diff. You may want to try some different feeds, etc. if you want your horse darker. I know that some people use Paprika to deepen the black, but that's not what I'm doing.