The trick to perfect hard boiled eggs every time is to never actually
boil them!
Here is what you do;
Place your eggs carefully in a pan, single layer only, and cover with
water to at least one inch above the eggs
Cover the pan and bring to a boil. As soon as it reaches a boil,
remove pan from heat immediately and
allow eggs to stand, for 15 to 20 minutes.
This will give you the perfect egg every time, and you will not have the
graying of the yoke that is the result of over cooking!!
Other tips...
New eggs do not peel well, older eggs peel more easily.
Use a needle to place a hole at each end of the egg and then blow out
the white and yolk if you'd like to keep your decorated eggs forever.