Why is my whey always a different color? This is my third jar. The powder has been a different color in each jar. Is this normal?

Yes, the different colors of Promix are all normal!  Our Promix formula has always been the same, and we source from the same farms and the same grass-fed cows for every batch.  Whey protein is a natural product, so each batch will vary slightly in taste, texture, color, etc. based on a variety of factors, including how much grass the cows are eating, the weather, etc.  The difference in color between batches is also based on the color of the cheese from which the whey is derived during the cheese making process.  Grass-fed milk naturally has a slight yellow color because of the extra beta carotene found in the milk of grass-fed cows.  The dark yellow color in some batches of Promix is from the natural annatto color used in making yellow cheeses, whereas the whiter color is from the white cheese batches.