The egg was used in Pagan celebrations of Spring as a symbol of the rebirth of the earth (just as new life emerges from an egg when the chick hatches out) which was then adopted by Christians. The old tradition consists of dying or painting chicken eggs while modern habit is to substitute chocolate eggs.
Persians have been painting eggs for Nowruz, their New Year celebration which falls on the Spring equinox, for at least 2500 years. The walls of Persepolis in Iran carry sculptures showing people bringing eggs for Nowruz to the King.
As a modern society, let’s take great pride in preserving the world’s heritage by celebrating such an old tradition.