O & H Bloodstock hit another home run when they sold Hip 156, a striking chestnut colt by Mr. Greeley, for $500,000 at the Keeneland April Two-year-old in training sale.   This was the highest priced son of Mr. Greeley in the sale.  The colt, who worked in the blazing time of :21 1/5, was purchased by leading buyer B. Wayne Hughes.