When crafting colored names or attaching runes to items to change enchant colors if you input more than a single item (such as a stack of runes or dye) it will eat the entire stack.

This is due to not setting the material cost in the anvil event, and so is easily solved by setting it to 1.

    private int materialCost; // The number of items from the right slot to be consumed during the repair. Leave as 0 to consume the entire stack.

    public void setMaterialCost(int materialCost) { this.materialCost = materialCost; }