An egg’s shell color doesn’t indicate the quality or nutritional value of an egg, but rather the breed of the hen that laid it. Hens with white feathers tend to lay white eggs and hens with red feathers tend to lay brown eggs.
The color of an egg yolk is determined by a hen’s diet. Like shell color, it has nothing to do with an egg’s nutritional value. If you crack open your egg to discover a dark yellow yolk, the hen was probably fed green vegetables. A medium-yellow yolk would indicate a diet of corn and alfalfa while a light-yellow yolk could be the result of eating wheat and barley.
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