Preschoolers are usually able to distinguish among different colors or shapes. Present them with an activity in which they must pick out something with a color or shape that is different from the other items in a group of similar items. For example, they could find the one green candy in a box of chocolates, or they could sort through a box of fruit to find the fruit that is larger than the rest, such as a Valencia orange in a box of clementines.
Once the children have mastered finding a unique object, they can begin to explore patterns. Show them scarves or woven bracelets that have similar patterns and ask them to identify the one with a different pattern. This activity requires more thought than simply finding an object that is different because the scarves or bracelets can have different colors, but the same pattern. As a result, the preschoolers will have to learn to think beyond the simple differences in color or size.
Learning to respect and value diversity is important for preschoolers because they are just learning to associate with people who are not in their family. Ask the children to describe one characteristic about themselves that is different from the other students. Preschoolers will probably choose the obvious differences, such as their skin or hair color, but these surface differences lend themselves to a discussion of how people can look different, but have many similarities. For example, Alicia might have black hair and Julie might have red hair, but they both like dogs and the color pink.
When the students are comfortable with exploring their own unique characteristics, they can learn about some unique features of the world around them. For example, bring in a Venus flytrap. Preschoolers are often astonished to learn that some plants eat insects. Discuss how this characteristic is unique to a particular class of plants. Other examples of unique items include hairless cats or mice, or blue corn.