Dye adds color to leather. There are two common varieties of dye: alcohol-based and oil-based (which is usually referred to as leather stain). Generally speaking, dye is used in the creation and repair of leather. Everyday leather and boot care usually does not require dye applcation, although dye is often useful for repair of significantly worn spots on boots. Dye may also be required in cases where the leather is to be completely stripped down and refinished, but this is an unusual case.