Salt blocks are available to producers in a variety of different colors. This variety is something any trip to your local feed store can tell you. Each color represents different situations in which they are needed.
The specific color of the block will tell you two things about it. The first is what kind of nutrients are present in the block. The second is what kind of use it is intended for. Such as the yellow sulfur block or the basic white salt block; there are many different options to go with.
With the different varieties out there, it can be confusing as to which block is best for you. Not to mention, much information on the subject can be confusing and conflicting. The one that is best for you will depend on what mineral(s) are deficient in your particular option. Also, what you want to accomplish will also play a factor in this decision.