Keep the sweat washed off!!!
This summer, I've really jumped on what I can to keep my geldings coat healthy and it's normal rich, dark bay color naturally, since he sweats too much under a fly sheet in the crazy heat and humidity.
It's typical. They're going to sweat in the summer to try and cool their bodies down. Of course, it's natural survival. Sweat, is full of salt. When you have an abscess, what do you do- soak it in salt to help dry it out. So what do you think it's doing to the coat and skin?
This summer, with the help of paprika, he is his dark bay self, and gleaming even if he hasn't been groomed in forever. After every ride, I always wash him off with water, and he always goes and rolls in the dirt afterwards. The next day, you wouldnt even know it. Dirt just slides right off of him. :)