To the average fan, every racehorse might seem pretty much the same. They pace or trot, go to the lead or come from behind, and are gray, bay, brown, chestnut, black or perhaps roan. But for trainers, every horse has a distinct personality, some more winning than others, in more ways than one. Brewster Burns interviews horsemen and women at the Windsor Fair about the horses that poses particular challenges to them during their careers.