Typically I have found that darker kidneys come from healthier animals. Ones with a rich deep dark color usually have a more favored flavor. I have had ones that are extremely pale and without color, they almost always taste horrid and I will not eat them. I would be personally weary of the light one in the picture!
Also Amish labeling means nothing! Ive seem some God Awful stuff come from the Amish farms in my area and wouldn't trust some guys claim as to its source without any other verification.
Its more common in my part of the world to find animals that fall somewhere in between dark and light..... often there is a lighter outer layer with the core color being much darker. To me this indicates that there may be some environmental stress, causing some damage to the outside layers, while the core maintains healthy function. Its not ideal, but sometimes you have to settle for whats available
I have seen this phenomenon in many animals while butchering at a commercial plant..hogs, lambs, cows, goats, deer....I have often wondered at the cause, and have suspected an number of factors to be in play that would cause "grass fed" animals to show signs of kidney stress.
Poor water quality such as municipal water that has been treated, but also stagnant swampy water on farms without fresh springs and streams, as well as polluted wells and streams....
Deficient land that is over grazed or cut will tend to be deficient in certain minerals needed for good overall health, and such land that has been depleted of its essential minerals makes animals more prone to accumulate toxic organ damaging elements such as cadmium, lead and aluminum....
