The color of the shell has nothing to do with the hen's health, the egg's quality, or the egg's nuritional value. Shell color is only determined by the breed of the hen; certain breeds lay brown eggs and others lay white.
Regardless of the color, check inside the carton for uncracked shells when egg shopping. Always purchase eggs before the "sell by" or expiration date if stamped on the carton. Once home leave eggs in their original carton and place them in the coldest part of the refrigerator. Eggs should never be stored in the refrigerator door because they will get warmer each time the door is opened, causing fast spoilage. For best quality, use eggs within 3 to 5 weeks after the date you purchase them. Even if the "sell by" date expires during that length of time, the eggs are still safe to eat.
For more information on preparing hard-boiled eggs, check out MissouriFamilies.org