Is it ok to buy ';pigment'; for your eyeshadow or does it need to be mixed?

I am looking at some makeup on ebay, MAC, and they are all called ';pigments';...will that be the same as my other MAC eyeshadow I have bought at the store?Is it ok to buy ';pigment'; for your eyeshadow or does it need to be mixed?
Pigments are concentrated color powders which can be used on the cheeks, lips, eyes, etc. They are a multipurpose cosmetic and can be used either alone or mixed with other products (such as with a clear lip gloss to tint it).Is it ok to buy ';pigment'; for your eyeshadow or does it need to be mixed?
I think pigments enhance your existing shadow. They are usually shiney/glittery. Useing a regular color as a base, then brush the pigment over the applied shadow ';enhances'; the look.