Besides the association with Jesus and the Passion Cycle, April is a time traditionally associated with spring and renewal in nature. An objective, visual, non-religious approach to the theme of spring in a learning environment that has nothing to do with Christianity is the coloured and decorated Easter Egg.
Tinted eggs go back much father than Biblical traditions, where they still had a connection to gravesites. In Africa and Mesopotamia, silver and gold eggs were in use at gravesites since antiquity. Today, Christian communities typically use colored eggs to symbolize the suffering of Jesus.
Whatever the reason, the coloured egg became an item that represented springtime.