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Little Blue and Little Yellow

by Leo Lionni


Little Blue and Little Yellow addresses several distinct concepts in philosophy: friendship, knowledge, identity, and the material constitution of things.

Instead of staying at home, Little Blue went out looking for his friend Little Yellow. They played together, had a lot of fun, and ended by looking like Little Green. When this happened, their parents couldn’t recognize them. The story is a journey in which the parents of Little Blue and Little Yellow and the readers realize what actually happens when blue and yellow mix.

Read aloud video by Sunshine Stories

Guidelines for Philosophical Discussion

Leo Lionni’s seemingly simple Little Blue and Little Yellow is packed with philosophical content and raises questions about multiple philosophical issues. While all the parts are interconnected and overlapping, the questions are divided thematically into three parts. Each part addresses a distinct concept in philosophy: friendship, knowledge, identity, and the material constitution of things. You can talk about any or all of them.

When Little Blue and Little Yellow hug each other, they merge into Little Green. Since they are best friends, their new color represents a merging of their two individual colors. This raises the question of what friendship is. Do friends have to become completely like each other to be good friends? If not, then what do they have to have in common to be friends? Can you be friends with someone with whom you share no common interest? Is a person who is really different from you actually a better candidate for friendship because their differences might provide lots of interesting things to discuss? These questions can lead to a more abstract discussion of why a person needs friends in her life. Could a person lead a fulfilled life even if she had no friends? These are significant philosophical issues that play a crucial role in children’s lives.

In epistemology (the study of knowledge), knowledge is classified as justified true belief. The story brings up the basic yet important issue of the nature of our beliefs and how new information impacts our beliefs. When the parents assert that Little Green is not Little Blue, they exhibit their belief about their child. This begs the question: is their belief justified and true? That is: did Mama and Papa Blue have the knowledge that Little Green was not Little Blue? Most philosophers would argue that this was simply a belief that was not true or justified. Epistemology tries to understand how we know the things we know. Additionally, it tries to ensure that the things we know are true, because otherwise, they are just beliefs. For example, the book raises the question of whether is it true that Green is not Little Blue. Lionni leaves the decision to the reader. Additionally, the beliefs we hold are molded by the information we have. Once the parents hugged the other color and witnessed what happened, they understand better. The acquisition of new information can have an impact on what we think and can change our beliefs.

The formation of Little Green raises questions about what things are made up of. Metaphysics, the study of the nature of reality, deals with this issue of material constitution. Philosophers are divided in their views on this topic. Some believe that parts are more important than the whole. I will explain this by using a simple example. When you make vegetable soup, the constituents are the vegetables and the broth. The soup is simply a different form of the two put together. This illustrates that things only change from one form to another and never go in or out of existence. This concept is known as mereology in philosophy. The alternative view is that the whole is more important than the constituents. This is illustrated by the example of mixing blue with yellow to create green. The parts cease to exist when the whole is created. Once you mix them, blue and yellow stop existing, and a new color green is created. In the story, this concept is questioned when Green is created, but Blue still feels like Blue. The story raises the question of which category the creation of green goes under but leaves the decision to the reader.

What makes Little Blue who he is? This raises questions about the fourth concept the book deals with: identity. What makes a thing what it is (its identity) can be understood by thinking of how much of it you can change before it becomes something new. This issue is dealt with in metaphysics. Philosophers have tried to understand how much a thing can change before it becomes something different. They have done this by dividing the properties of a thing into two categories: essential properties and accidental properties. Essential properties are those that, if changed, the thing is no longer the same. Accidental properties are those that can be changed without changing the nature of the thing. While most philosophers agree on this division, the disagreement arises on which properties go under each category. For instance, some people might think that the taste of an apple is an essential property. But rotten apples that don’t taste like fresh apples are still apples. Some people might think that the shape of an apple is what is essential, yet some apples are deformed and they are still apples. Therefore, while philosophers agree that the two categories exist, it is hard, if not impossible to know what property goes under which category. In the book, the color of Little Blue is what makes him ‘little blue’, but when he becomes green, he still goes to the house that Little Blue considers home. He looks different but feels the same. The story raises this question about identity but leaves the decision to the reader.

Questions for Philosophical Discussion


Little Blue has many friends, but his best friend is Little Yellow.

  1. Do you think that you need to become exactly like your best friend?
  2. Do friends have to have things in common? What things?
  3. Is it better for friends to be like each other or different from one another?
  4. Is having friends important to your happiness?


When Little Blue found Little Yellow they hugged each other happily.

  1. What happened when Little Blue hugged Little Yellow?
  2. Why didn’t Papa and Mama Blue recognize Little Blue?
  3. When Mama and Papa Blue think that Little Green is not Little Blue, were they right?

When Mama and Papa Blue hugged Little Yellow, they became green, and then they realized what had happened.

  1. How did the parents realize what had happened?
  2. Can you think of a situation where things are not the way they look?
  3. There is a saying that “seeing is believing.” What do you think this means? Do you agree?
  4. Can you think of a situation when you thought a certain way, but when you found out more about the thing you changed the way you thought about it?

Material Constitution

Little Blue and Little Yellow were sad when their parents didn’t recognize them, and they cried big blue and yellow tears. Now think of things like vegetable soup and paint.

  1. Can you think of something that is made up of more than one thing?
  2. Can you separate the vegetables from the broth?
  3. Does something happen to the vegetables and the broth when you mix them to make soup?
  4. Can you separate yellow paint from blue paint when you mix the two to make green?
  5. Does something happen to the blue and yellow paint that you mix?
  6. What happened to Little Blue and Little Yellow when they became green?
  7. Do Little Blue and Little Yellow still exist when they become green, or do they just change?
  8. Little Blue and Little Yellow cried blue and yellow tears and became themselves again. What would happen if they were like paint and couldn’t separate themselves once they were mixed?
  9. What makes “green” what it is?
  10. Is “green” something totally new, or is green a changed version of blue and yellow?


They cried and cried until they were all tears, and when they finally pulled themselves together, they were Little Blue and Little Yellow again.

  1. Imagine that I paint a paper orange. Is it still the same paper?
  2. Now imagine I burn that paper. Is it still the same paper?
  3. Can you think of something that changes its shape or form but is still the same thing?
  4. Does the thing remain the same once it changes?
  5. Do you think people change as they get older?
  6. Do they become something new when they change?
  7. Now that Little Blue has become green, is Little Blue different?

Original questions and guidelines for philosophical discussion by Hina Jawaid and Thomas Wartenberg. Edited June 2020 by The Janet Prindle Institute for Ethics.

Find tips for leading a philosophical discussion on our Resources page.

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Back to All Books Illustrated book cover for Little Blue and Little Yellow featuring a blue spot and a yellow spot with rough edges. They intersect to form green on a white background. Above them is a rough, orange border. Below them is a rough, black border. Download & Print Email Book Module

About the Prindle Institute

As one of the largest collegiate ethics institutes in the country, the Prindle Institute for Ethics’ uniquely robust national outreach mission serves DePauw students, faculty and staff; academics and scholars throughout the United States and in the international community; life-long learners; and the Greencastle community in a variety of ways. In 2019, the Prindle Institute partrnered with Thomas Wartenberg and became the digital home of his Teaching Children Philosophy discussion guides.

Further Resources

Some of the books on this site may contain characterizations or illustrations that are culturally insensitive or inaccurate. We encourage educators to visit the Association for Library Service to Children’s resource guide for talking to children about issues of race and culture in literature. They also have a guide for navigating tough conversations.  PBS Kids’ set of resources for talking to young children about race and racism might also be useful for educators.

Philosophy often deals with big questions like the existence of a higher power or death. Find tips for leading a philosophical discussion on our resources page.

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