Nothing is more discouraging than having your horse greet you everytime with the flight response of going to the far corner and turning his butt toward you. On top of that it is dangerous to approach a horse in this manner. Correcting the behavior may be as simple as always having a treat to put into the feed bucket as you stand beside it and a gentle voice. Some horses however will not respond to this simple cajoling. Being a vet I have a lot of equine friends that act this way. Here's how I would handle the situation.

Whenever I enter a stall with a horse that acts this way I carry a lunge whip (the whip portion taped against the stiff rod) and a treat. When the horse turns his butt to me, I begin tapping his rear lightly, out of reach of a kick. I continue to tap until he turns sideways with his butt away from me, the neutral position, and pointed to the far corner. Then I stop and praise him until he is calm in this position. I then take a step toward him. I keep my head and arms down and my voice reassuring. If I reach his head, I then gently reach up and scratch his head. Once he is calm, I return to the outside of the stall and repeat this several times. At first when I approach he will frequently turn the butt toward me again. The second the rear end BEGINS to swing my way I begin tapping again as I quietly step back to my original position by the stall door. The second the rear end BEGINS to turn away I stop. As long as the colt is in a neutral position and nonthreatening, I give him all the positive reinforcement my voice can muster.