For a while, papal edicts banned the eating of eggs during the 40-day period of Lent that leads up to Easter. Of course no one told the hens, so there were plenty of eggs to use when the Lenten fast was over. Hard-boiling the eggs helped them last longer. How people came to color eggs is not known, but the tradition is very old. Ukrainians use a form of batiking called Pysanka to produce the colorful, intricate designs found on their Easter eggs.
Picture of Pysanka Eggs supplied by Luba Petrusha