Hardboiled Eggs: Yellow hardboiled eggs
To cook hardboiled eggs with no green ring around the yolk (which occurs when the egg is cooked for too long or at too high a temperature), place the eggs in a pan large enough to hold them in a single layer and cover them with cold water by an inch. Bring to a boil, and as soon as the water boils, cover the pan and remove it from the heat. Let the eggs sit in the covered pan for about 15 minutes, then peel. (Thanks, Jane!)
Marcella spends several months a year in the Colorado Rockies at about 7500 feet. Because water boils at a lower temperature at altitude, you must keep the egg in the hot water for a longer period of time. At 7500 feet, add about half again as much time, so keep the egg in the water for between 20-25 minutes. You will have to experiment at different altitudes.
Fresher eggs are harder to peel, so try to use older eggs when hard-boiling.