What decorating Easter Eggs has to do with K/r selection theory? You probably remember that K/r-selection theory stands for a selection in reproductive behavior including mating. Maybe you also know that this theory to a certain degree is applicable to humans too. Though still discussed quite controversially, I like the idea that humans can be divided into those who follow the r-mating strategy (many offspring no matter what quality) and those who prefer the K-strategy (height quality offspring no matter how few).
Evolutionary biologists discovered that the r-strategy evolved among species that live with abundant resources while K-strategy is typical of environments in which resources are scarce. Different human societies like species live in environments which offer a quite different supply of resources, so their cultures differ in respect to the mating behavior they encourage. Their traditions and customs often reflect that.
I venture to claim that those societies whose culture includes an artful decoration of Easter Eggs are more likely to favor K-selection, because if that custom is followed by an entire community and the products exchanged and compared that automatically creates a competition in which the height quality mates win an advantage. Well and that’s typical of K-selection.