Yep, this heat is brutal. I am up here in the TX panhandle so I completely understand. Make sure that they have cool, clean water, good food, and shade available at all times. I agree with trying to get the colt out of that stall. The bad things about barns in the summertime is that they are almost always stifling, even with fans going so open air is best. I also take time every day to spray down all my horses that come to the fence for it (my black ones especially) though the ones who don't volunteer show no signs of distress. Watch for signs of them getting too hot and if that happens, then take them to a shaded area and spend time spraying them with cool water to get their core temp down. Always scrape the excess water off afterward because leaving it on is like leaving them under a blanket.