Blood spots are caused when a blood vessel on the yolk surface ruptures during formation. This is usually detected in the grading process detection. Actually, a blood spot indicates a fresh egg. You can eat them. Just remove the spot with a knife tip.
Egg shells are porous.
They have about 17,000 pores. Eggs age more in one day at room temperature than in one week in the refrigerator. White eggs come from white feathered hens with white ear lobes. Brown eggs come from red feathered hens with red ear lobes. Diet determines yolk color.