Fading?

So my horse Tiger is a Palomino paint. I keep him in the stall during the day because his spots fade and he burns. Well I notice still when he sheds his winter coat that his spot on his chest turns dark.. almost like a brownish gray. Sometimes there is no way I can put him in the stall now and then so he will stay out in the pasture and sweat. Usually his neck is the first to sweat.

Well is there anything I can put on his coat to help his spots get dark and stand out more? Or something I can feed him? I'm thinking about trying apple cider vinegar in his feed.. What do you think? I want to focus on halter classes this year so any advice would be helpful :)

Sorry! Forgot to post the picture:

*look at the spot on his chest.. see, not really palomino anymore

Here's a few more pictures.. the second one is Tiger with his winter coat. You can see his spot is clearly palomino there.

There's nothing you can do to darken him up now. To keep him from getting lighter, use a protective fly sheet with a neck cover that will block 70% of the sun's rays or more. That way he can be turned out normally or more often (I am not a fan of stalling horses).

You can try feeding him a supplement to darken the coat, like "Gold as Sun." Coat Enhancers

Plain flax meal is also great for coat health.