Q: Why are there so many different colored salt blocks for livestock?      

A: Each color of salt block has different minerals in it; as well, there are many kinds of salt, including sulfur, plain, iodized, trace mineral, and trace mineral with selenium. The most important reason for using any salt is to encourage your horse to drink. Dehydration has a profound and immediate impact on the well-being of your horse, more than the lack of any other nutrient. When using any salt, it’s important to provide fresh and clean water at all times. The safest color of salt to start with is white, but check with your veterinarian as to which salt is best for your horse’s needs. 

—Lee's Feed and Western Store - Shingle Springs, CA