I brought these Tortilla chips to Pre-School for a snack: they were purple, red, and regular. They all tasted exactly the same. We gave each child a handful of chips, making sure each one received every color. An interesting thing began to happen - apparently the red chips tasted funny. I wanted to see what would happen, and sure enough, other preschoolers started having problems with various colors. Only one child said, "Hey! They all taste the same!," almost as if I had tricked him by giving him chips that all tasted the same. Only one other child affirmed that they did indeed all taste the same and argue his point.
I'm sure there is a biblical truth that can be added to this.. maybe you have some ideas?