With the Diamond Apple, you could customize your horse's coat. You could choose from amongst various colours and marks, allowing your horse to have an uncommon coat.
This item was removed due to many errors. Players were having difficulties creating the coats, as well as certain browsers not supporting the feature.
To this day, horses with the Diamond Apple still exist on the game. They can be found in the Sales but cost numerous amouts of equus and passes. They have become very rare and hard to find.
This item is no longer available in the Black Market.