From the brains behind brains on, this is the Moment of Um. Moment of Um comes to you from APM Studios. I'm Blink, and I'm a talking eyeball.

Um. As an eyeball, it's my job to soak in all the light from the world around you

and turn it into information that I send down to your brain for processing.

Now, Brain and I are pals.

Love their work.

Really admire their organizational skills.

But sometimes it's hard for an artist like me to communicate

with such a, how shall I say this? Stickler for information? And brain does tend to overthink

everything. Like the other day, I was trying to send a gorgeous shade of red that I saw in some garden flowers.

Next thing I know, brain is spiraling off into a whole galaxy of questions.

What kind of flowers are those? What kind of red are they? Is it a yellowy red? Or more like a purpley red?

Do other eyeballs see that flower as red? How many colors are

there? It was a lot. But it did remind me of a great question that my friend Avi sent in.

Hi, my name is Avi and I'm from San Somo, California.

My question is, how many colors can I see?

Scientists estimate that the number of colors that most of us can discriminate between is about 5 million.

So we see colour when our eyes respond to light that's emitted by light sources or reflected by materials.

My name is Stephen Westland. I'm a professor at the University of Leeds

and my title is Professor of colour science and technology.

The eye contains special cells called cones that respond to different wavelengths or colours of light,

and they send signals to the brain.

We know that some people don't see colours exactly the same of the rest of us

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